Digital focus and tracking servo system with multi-zone calibration

ABSTRACT

A multi-zone calibration system is disclosed. The multi-zone calibration system calibrates the operating parameters of an optical disk drive over a plurality of zones over an optical media. The optical media, in addition, can have writeable and premastered portions. The operating parameters can be calibrated for each of the media types in each of the zones. Additionally, the operating parameters can be calibrated for each type of operation (e.g., read or write) in each zone.

RELATED APPLICATIONS

This application is related to provisional application Ser. No.60/264,351 filed Jan. 25, 2001, entitled “Optical Disk Drive ServoSystem,” by Ron J. Kadlec, Christopher J. Turner, Hans B. Wach, andCharles R. Watt, from which this application claims priority, hereinincorporated by reference in its entirety.

CROSS-REFERENCE TO CD-ROM APPENDIX

CD-ROM Appendix A, which is a part of the present disclosure, is aCD-ROM appendix consisting of twenty two (22) text files. CD-ROMAppendix A is a computer program listing appendix that includes asoftware program executable on a controller as described below. Thetotal number of compact disks including duplicates is two. Appendix B,which is part of the present specification, contains a list of the filescontained on the compact disk. The attached CD-ROM Appendix A isformatted for an IBM-PC operating a Windows operating system.

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent files or records, but otherwise reserves all copyrightrights whatsoever.

These and other embodiments are further discussed below.

BACKGROUND

1. Field of the Invention

The present invention relates to an optical disk drive and, inparticular, an calibration of a servo system for an optical disk driveover multiple zones.

2. Discussion of Related Art

The need for compact data storage is explosively increasing. Theexplosive increase in demand is fueled by the growth of multimediasystems utilizing text, video, and audio information. Furthermore, thereis a large demand for highly portable, rugged, and robust systems foruse as multimedia entertainment, storage systems for PDA'S, cell phones,electronic books, and other systems. One of the more promisingtechnologies for rugged, removable, and portable data storage is WORM(write once read many) optical disk drives.

One of the important factors affecting design of an optical system (suchas that utilized in a WORM drive) is the optical components utilized inthe system and the control of actuators utilized to control the opticalsystem on the disk. The optical system typically includes a laser orother optical source, focusing lenses, reflectors, optical detectors,and other components. Although a wide variety of systems have been usedor proposed, typical previous systems have used optical components thatwere sufficiently large and/or massive that functions such as focusand/or tracking were performed by moving components of the opticalsystem. For example, some systems move the objective lens (e.g. forfocus) relative to the laser or other light source. It was generallybelieved that the relatively large size of the optical components wasrelated to the spot size, which in turn was substantially dictated bydesigns in which the data layer of a disk was significantly spaced fromthe physical surface of the disk. A typical optical path, then, passedthrough a disk substrate, or some other portion of the disk, typicallypassing through a substantial distance of the disk thickness, such asabout 0.6 mm or more, before reaching a data layer.

Regardless of the cause being provided for relative movement betweenoptical components, such an approach, while perhaps useful foraccommodating relatively large or massive components, presents certaindisadvantages for more compact usage. These disadvantages include arequirement for large form factors, the cost associated withestablishing and maintaining optical alignment between components whichmust be made moveable with respect to one another, and the powerrequired to perform operations on more massive drive components. Suchalignment often involves manual and/or individual alignment oradjustment procedures which can undesirably increase manufacturing orfabrication costs for a reader/writer, as well as contributing to costsof design, maintenance, repair, and the like.

Many early optical disks and other optical storage systems providedrelatively large format read/write devices including, for example,devices for use in connection with 12 inch (or larger) diameter disks.As optical storage technologies have developed, however, there has beenincreasing attention toward providing feasible and practical systemswhich are of relatively smaller size. Generally, a practical read/writedevice must accommodate numerous items within its form factor, includingthe media, media cartridge (if any), media spin motor, power supplyand/or conditioning, signal processing, focus, tracking or other servoelectronics, and components associated or affecting the laser or lightbeam optics. Accordingly, in order to facilitate a relatively smallform-factor, an optical head occupying small volume is desirable. Inparticular, it is desirable that the optical head have a small dimensionin the direction perpendicular to the surface of the spinning media.Additionally, a smaller, more compact, optical head provides numerousspecific problems for electronics designed to control the position andfocus of the optical head.

Additionally, although larger home systems have little concern regardingpower usage, portable personal systems should be low power devices.Therefore, it is also important to have a system that conserves power(e.g., by optically overfilling lenses) in both the optical system andthe electronic controlling system.

Therefore, there is a need for an optical head and optical media drivesystem with a small form factor and, in addition, a servo system forcontrolling the optical head and optical drive system so that data canbe reliably read from and written to the optical media.

SUMMARY

In accordance with the present invention, operating parameters of adigital focus and tracking servo system of an optical disk drive arecalibrated over a plurality of zones over an optical media. The opticaldisk drive system includes a spin motor on which an optical media ispositioned, an optical pick-up unit positioned relative to the opticalmedia, an actuator arm that controls the position of the optical pick-upunit, and a control system for controlling the spin motor, the actuatorarm, and the laser. The control system can include a read/write channelcoupled to provide control signals to a servo system.

The optical media can be a relatively small-sized disk with readabledata present on the surface of the disk. Furthermore, the optical diskmay have a pre-mastered portion and a writeable portion. Thepre-mastered portion is formed when the disk is manufactured andcontains readable data such as, for example, audio, video, text or anyother data that a content provider may wish to include on the disk. Thewriteable portion is left blank and can be written by the disk drive tocontain user information (e.g., user notes, interactive status (forexample in video games), or other information that the drive or user maywrite to the disk). Because there may be optical differences, forexample in reflectivity, and in the data storage and addressingprotocols between the pre-mastered portion of the disk and the writableportion of the disk, a control system according to the present inventionmay have different operating parameters in the different areas of thedisk.

The optical pick-up unit can includes a light source, reflectors,lenses, and detectors for directing light onto the optical media. Thedetectors can include laser power feed-back detectors as well as datadetectors for reading data from the optical media. The optical pick-upunit can be mechanically mounted on the actuator arm. The actuator armincludes a tracking actuator for controlling lateral movement across theoptical media and a focus actuator for controlling the position of theoptical pick-up unit above the optical medium. The tracking and focusactuators of the optical pick-up unit are controlled by the controller.

The servo system includes various servo loops for controlling theoperation of aspects of the optical disk drive, for example the spinmotor, the optical pick-up unit, and the controller. The servo loops,for example, can include combinations of a tracking servo loop and afocus servo loop.

A multi-zone calibration according to the present invention can includepositioning the optical pick-up unit over a current zone, the currentzone being one of the plurality of zones over the optical media,performing calibration algorithms to optimize operating parameterswithin the current zone, and proceeding to the next zone if not all ofthe zones have been calibrated. In some embodiments, the calibrationalgorithms can include combinations of a focus error signal offsetcalibration, a focus error signal gain calibration, a tracking errorsignal offset calibration, a tracking error signal gain calibration, aninverse non-linearity calibration, a notch filter calibration, a loopgain calibration, or any other calibrations that adjust operatingparameters for an optical disk.

In some embodiments, operating parameters are adjusted for multiplemedia types and multiple operating conditions within some of theplurality of zones. In some embodiments, the plurality of zones can bedefined by the media types on the optical media.

A disk drive according to the present invention includes an opticalpick-up unit; an analog processor coupled to receive signals fromdetectors in the optical pick-up unit and provide digital signals; atleast one processor coupled to the digital signals, the processorcalculating a control signal; and a driver coupled to control a positionof the optical pick-up unit in response to the control signal. Theprocessor executes an algorithm that calibrates operating parametersover a plurality of zones by positioning an optical pick-up unit over acurrent zone, the current zone being one of the plurality of zones on anoptical media, performing calibration algorithms to optimize operatingparameters within the current zone, and proceeding to a next zone, thenext zone being another one of the plurality of zones, unless all of theplurality of zones have been calibrated.

These and other embodiments of the invention are further described belowwith respect to the following figures.

SHORT DESCRIPTION OF THE FIGURES

FIG. 1A shows an embodiment of an optical drive according to the presentinvention.

FIG. 1B shows an example of an optical media that can be utilized withan optical drive according to the present invention.

FIG. 2A shows an embodiment of an optical pickup unit mounted on anactuator arm according to some embodiments of the present invention.

FIG. 2B shows an embodiment of an optical pick-up unit according to someembodiments of the present invention.

FIG. 2C illustrates the optical path through the optical pick-up unit ofFIG. 2B.

FIG. 2D shows an embodiment of optical detector positioning of theoptical pick-up unit of FIG. 2B.

FIGS. 2E and 2F show simplified optical paths as shown in FIG. 2C.

FIGS. 2G, 2H, 2I, 2J, 2K and 2L illustrate development of a focus errorsignal (FES) as a function of distance between the optical pick-up unitand the surface of the optical media in some embodiments of the presentinvention.

FIGS. 2M, 2N, 2O, 2P, 2Q, and 2R illustrate development of a trackingerror signal (TES) as a function of position of the optical pick-up unitover the surface of the optical media in some embodiments of the presentinvention.

FIG. 3A shows a block diagram of a servo system control system of anoptical drive according to some embodiments of the present invention.

FIG. 3B shows a block diagram of a preamp of FIG. 3A.

FIG. 4 shows a block diagram of an embodiment of the controller chipshown in the block diagram of FIG. 3A according to some embodiments ofthe present invention.

FIGS. 5A and 5B show a function block diagram of embodiments of a focusand tracking servo algorithms according to some embodiments of thepresent invention.

FIG. 5C shows an example transfer function for a low frequencyintegrator as shown in FIGS. 5A and 5B.

FIG. 5D shows an example transfer function for a phase lead as shown inFIGS. 5A and 5B.

FIGS. 5E and 5F shows an example of a tracking skate detector accordingto some embodiments of the present invention.

FIG. 5G shows an embodiment of a direction sensor according to someembodiments of the present invention.

FIG. 6 shows an embodiment of a tracking acquisition algorithm executedwith the algorithms shown in FIGS. 5A and 5B.

FIGS. 7A, 7B, 7C, and 7D show an embodiment of a focus acquisitionalgorithm executed with the algorithms shown in FIGS. 5A and 5Baccording to some embodiments of the present invention.

FIGS. 8A and 8B shows an embodiment of a multi-track seek algorithmaccording to some embodiments of the present invention.

FIGS. 9A and 9B show an embodiment of a multi-track seek algorithmexecuted with the algorithms illustrated in the functional block diagramshown in FIGS. 8A and 8B in some embodiments of the present invention.

FIG. 9C illustrates the temporal hysterisis and amplitude hysterisis oftracking zero cross detection of FIGS. 9A and 9B.

FIGS. 10A and 10B show demonstrative control signals and a block diagramof a one-track jump algorithm of FIGS. 5A and 5B according to someembodiments of the present invention.

FIG. 11 shows an embodiment of the DSP firmware architecture forcontrolling and monitoring focus and tracking according to someembodiments of the present invention.

FIG. 12A shows a block diagram of an embodiment of a calibrationlifetime for a drive according to some embodiments of the presentinvention.

FIG. 12B shows a chart of parameters and when those parameters arecalibrated through the lifetime of an example drive according to someembodiments of the present invention.

FIG. 13A shows a block diagram of an embodiment of a calibrationalgorithm according to some embodiments of the present invention whichobtains calibration parameters over various media types and underdifferent conditions.

FIG. 13B shows a block diagram of an embodiment of a calibrationalgorithm according to some embodiments of the present invention.

FIG. 14A shows a block diagram of an embodiment of a calibrationalgorithm according to some embodiments of the present invention forcalibrating the detector input offset and gain values.

FIG. 14B shows a block diagram of an embodiment of a calibrationalgorithm according to some embodiments of the present invention forcalibrating the detector input offsets with light scattering.

FIGS. 15A and 15B show a block diagram of an embodiment of a FES gaincalibration algorithm according to some embodiments of the presentinvention and input signals measured or generated during thecalibration.

FIG. 16A shows an embodiment of a FES offset calibration algorithmaccording to some embodiments of the present invention.

FIG. 16B shows another embodiment of an FES offset calibration algorithmaccording to some embodiments of the present invention.

FIG. 16C shows a graph of the TES peak-to-peak signal as a function ofFES offset illustrating a calibration of the TES offset according tosome embodiments of the present invention.

FIG. 17 shows another embodiment of a FES offset calibration algorithmaccording to some embodiments of the present invention.

FIG. 18 shows an embodiment of a TES offset calibration algorithmaccording to some embodiments of the present invention.

FIG. 19 shows another embodiment of a TES offset calibration algorithmaccording to some embodiments of the present invention.

FIG. 20 shows an embodiment of a TES Gain calibration algorithmaccording to some embodiments of the present invention.

FIG. 21 shows an embodiment of a loop gain calibration algorithmaccording to some embodiments of the present invention.

FIG. 22 shows an embodiment of a Bode algorithm according to someembodiments of the present invention.

FIG. 23 shows an embodiment of a Fourier transform algorithm accordingto some embodiments of the present invention.

FIG. 24 shows an embodiment of a TES-FES crosstalk calibration algorithmaccording to some embodiments of the present invention.

FIG. 25 shows an embodiment of a notch filter calibration algorithmaccording to some embodiments of the present invention.

FIG. 26 shows an embodiment of a feed-forward correction algorithmaccording to some embodiments of the present invention.

FIGS. 27A and 27B show an embodiment of a zone-calibration algorithmaccording to some embodiments of the present invention.

FIG. 28 shows an embodiment of an inverse non-linearity calibrationalgorithm according to some embodiments of the present invention.

FIG. 29 shows an embodiment of a head load algorithm according to someembodiments of the present invention.

FIGS. 30A and 30B show examples of a tracking error signal over the barcode area.

FIG. 30C shows an example of a tracking error signal during a closetracking operation.

In the figures, elements having the same designation in multiple figureshave the same or similar functions.

DETAILED DESCRIPTION OF THE FIGURES

The present disclosure was co-filed with the following sets ofdisclosures: the “Tracking and Focus Servo System” disclosures, the“Servo System Calibration” disclosures, the “Spin Motor Servo System”disclosures, and the “System Architecture” disclosures; each of whichwas filed on the same date and assigned to the same assignee as thepresent disclosure, and are incorporated by reference herein in theirentirety. The Tracking and Focus Servo System disclosures include U.S.Disclosure Ser. Nos. 09/950,329, 09/950,408, 09/950,444, 09/950,394,09/950,413, 09/950,397, 09/950,914, 09/950,410, 09/950,441, 09/950,373,09/950,425, 09/950,414, 09/950,378, 09/950,513, 09/950,331, 09/950,395,09/950,376, 09/950,393, 09/950,432, 09/950,379, 09/950,515, 09/950,411,09/950,412, 09/950,361, 09/950,540, 09/950,519. The Servo SystemCalibration disclosures include U.S. Disclosure Ser. Nos. 09/950,396,09/950,360, 09/950,372, 09/950,541, 09/950,409, 09/950,520, 09/950,377,09/950,367, 09/950,512, 09/950,415, 09/950,548, 09/950,392, and09/950,514. The Spin Motor Servo System disclosures include U.S.Disclosure Ser. Nos. 09/951,108, 09/951,869, 09/951,330, 09/951,930,09/951,328, 09/951,325 and 09/951,475. The System Architecturedisclosures include U.S. Disclosure Ser. Nos. 09/951,947, 09/951,340,09/951,339, 09/951,469, 09/951,337, 09/951,329, 09/951,332, 09/051,931,09/951,850, 09/951,333, 09/951,331, 09/951,156 and 09/951,940.

Example of an Optical Disk Drive

FIG. 1A shows an embodiment of an optical drive 100 according to thepresent invention. Optical drive 100 of FIG. 1A includes a spindle motor101 on which an optical media 102 is mounted. Drive 100 further includesan optical pick-up unit (OPU) 103 mechanically controlled by an actuatorarm 104. OPU 103 includes a light source electrically controlled bylaser driver 105. OPU 103 further includes optical detectors providingsignals for controller 106. Controller 106 can control the rotationalspeed of optical media 102 by controlling spindle motor 101, controlsthe position and orientation of OPU 103 through actuator arm 104, andcontrols the optical power of the light source in OPU 103 by controllinglaser driver 105.

Controller 106 includes R/W processing 110, servo system 120, andinterface 130. R/W processing 110 controls the reading of data fromoptical media 102 and the writing of data to optical media 102. R/Wprocessing 110 outputs data to a host (not shown) through interface 130.Servo system 120 controls the speed of spindle motor 101, the positionof OPU 103, and the laser power in response to signals from R/Wprocessing 110. Further, servo system 120 insures that the operatingparameters (e.g., focus, tracking, spindle motor speed and laser power)are controlled in order that data can be read from or written to opticalmedia 102.

FIG. 1B shows an example of optical media 102. Optical media 102 caninclude any combinations of pre-mastered portions 150 and writeableportions 151. Premastered portions 150, for example, can be written atthe time of manufacture to include content provided by a contentprovider. The content, for example, can include audio data, video data,text data, or any other data that can be provided with optical media102. Writeable portion 151 of optical media 102 can be written onto bydrive 100 to provide data for future utilization of optical media 102.The user, for example, may write notes, keep interactive status (e.g.for games or interactive books) or other information on the disk. Drive100, for example, may write calibration data or other operating data tothe disk for future operations of drive 100 with optical media 102. Insome embodiments, optical media 102 includes an inner region 153 closeto spindle access 152. A bar code can be written on a portion of aninner region 153. The readable portion of optical media 102 starts atthe boundary of region 151 in FIG. 1B. In some embodiments, writeableportion 151 may be at the outer diameter rather than the inner diameter.In some embodiments of optical media 102, an unusable outer region 154can also be included.

An example of optical media 102 is described in U.S. application Ser.No. 09/560,781 for “Miniature Optical Recording Disk”, hereinincorporated by reference in its entirety. The R/W Data Processing 110can operate with many different disk formats. One example of a diskformat is provided in U.S. application Ser. No. 09/527,982, for“Combination Mastered and Writeable Medium and Use in Electronic BookInternet Appliance,” herein incorporated by reference in its entirety.Other examples of disk data formats are provided in U.S. applicationSer. No. 09/539,841, “File System Management Embedded in a StorageDevice;” U.S. application Ser. No. 09/583,448, “Disk Format forWriteable Mastered Media;” U.S. application Ser. No. 09/542,181,“Structure and Method for Storing Data on Optical Disks;” U.S.application Ser. No. 09/542,510 for “Embedded Data Encryption Means;”U.S. application Ser. No. 09/583,133 for “Read Write File SystemEmulation;” and U.S. application Ser. No. 09/583,452 for “Method ofDecrypting Data Stored on a Storage Device Using an EmbeddedEncryption/Decryption Means,” each of which is herein incorporated byreference in its entirety.

Drive 100 can be included in any host, for example personal electronicdevices. Examples of hosts that may include drive 100 are furtherdescribed in U.S. patent application Ser. No. 09/315,398 for RemovableOptical Storage Device and System, herein incorporated by reference inits entirety. Further discussions of hosts that may include drive 100 isprovided in U.S. application Ser. No. 09/950,516 and U.S. applicationSer. No. 09/950,365, each of which is herein incorporated by referencein its entirety. In some embodiments, drive 100 can have a relativelysmall form factor such as about 10.5 mm height, 50 mm width and 40 mmdepth.

FIG. 2A shows an embodiment of actuator arm 104 with OPU 103 mounted onone end. Actuator arm 104 in FIG. 2A includes a spindle 200 whichprovides a rotational pivot about axis 203 for actuator arm 104.Actuator 201, which in some embodiments can be a magnetic coilpositioned over a permanent magnet, can be provided with a current toprovide a rotational motion about axis 203 on spindle 200. Actuator arm104 further includes a flex axis 204. A motion of OPU 103 substantiallyperpendicular to the rotational motion about axis 203 can be provided byactivating actuator coil 206. In some embodiments, actuators 206 and 201can be voice coil motors.

FIGS. 2B and 2C show an embodiment of OPU 103 and an optical ray tracediagram of OPU 103, respectively. OPU 103 of FIG. 2B includes aperiscope 210 having reflecting surfaces 211, 212, and 213. Periscope210 is mounted on a transparent optical block 214. Object lens 223 ispositioned on spacers 221 and mounted onto quarter wave plate (QWP) 222which is mounted on periscope 210. Periscope 210 is, in turn, mountedonto turning mirror 216 and spacer 231, which are mounted on a siliconsubmount 215. A laser 218 is mounted on a laser mount 217 and positionedon silicon submount 215. Detectors 225 and 226 are positioned andmounted on silicon substrate 215. In some embodiments, a high frequencyoscillator (HFO) 219 can be mounted next to laser 218 on siliconsubmount 215 to provide modulation for the laser beam output of laser218.

Laser 218 produces an optical beam 224 which is reflected intotransparent block 214 by turning mirror 216. Beam 224 is then reflectedby reflection surfaces 212 and 213 into lens 223 and onto optical medium102 (see FIG. 1A). In some embodiments, reflection surfaces 212 and 213can be polarization dependent and can be tuned to reflect substantiallyall of polarized optical beam 224 from laser 218. QWP 222 rotates thepolarization of laser beam 224 so that a light beam reflected fromoptical media 102 is polarized in a direction opposite that of opticalbeam 224.

The reflected beam 230 from optical medium 102 is collected by lens 223and focused into periscope 210. A portion (in some embodiments about50%) of reflected beam 230, which is polarized opposite of optical beam224, passes through reflecting surface 213 and is directed onto opticaldetector 226. Further, a portion of reflected beam 230 passes throughreflecting surface 212 and is reflected onto detector 225 by reflectingsurface 211. Because of the difference in path distance between thepositions of detectors 225 and 226, detector 226 is positioned beforethe focal point of lens 223 and detector 225 is positioned after thefocal point of lens 223, as is shown in the optical ray diagram of FIG.2C through 2F.

In some embodiments, optical surface 212 is nearly 100% reflective for afirst polarization of light and nearly 100% transmissive for theopposite polarization. Optical surface 213 can be made nearly 100%reflective for the first polarization of light and nearly 50% reflectivefor the opposite polarization of light, so that light of the oppositepolarization incident on surface 213 is approximately 50% transmitted.Optical surface 211 can, then, be made nearly 100% reflective for theopposite polarization of light. In that fashion, nearly 100% of opticalbeam 224 is incident on optical media 102 while 50% of the collectedreturn light is incident on detector 226 and about 50% of the collectedreturn light is incident on detector 225.

A portion of laser beam 224 from laser 218 can be reflected by anannular reflector 252 positioned in periscope 210 on the surface ofoptical block 214. Annular reflector 252 may be a holographic reflectorwritten into the surface of optical block 214 about the position thatoptical beam 224 passes. Annular reflector 252 reflects some of thelaser power back onto a detector 250 mounted onto laser block 217.Detector 250 provides a laser power signal that can be used in a servosystem to control the power of laser 218.

FIG. 2D shows an embodiment of detectors 225 and 226 which can beutilized with some embodiments of the present invention. Detector 225includes an array of optical detectors 231, 232, and 233 positioned on amount 215. Each individual detector, detectors 231, 232, and 233, iselectrically coupled to provide raw detector signals A_(R), E_(R) andC_(R) to controller 106. Detector 226 also includes an array ofdetectors, detectors 234, 235 and 236, which provide raw detectorsignals B_(R), F_(R), and D_(R), respectively, to controller 106. Insome embodiments, center detectors 232 and 235, providing signals E_(R)and F_(R), respectively, are arranged to approximately optically alignwith the tracks of optical media 102 as actuator arm 104 is rotatedacross optical media 102. In some embodiments, the angle of rotation ofdetectors 225 and 226 with respect to mount 215 is about 9.9 degrees andis chosen to approximately insure that the interference patterns oflight beam 225 reflect back from optical media 102 is approximatelysymmetrically incident with segments 231, 232, 233 of detector 225 andsegments 234, 235 and 236 of detector 226. Non-symmetry can contributeto optical cross-talk between derived servo signals such as the focuserror signal and the tracking error signal.

A focus condition will result in a small diameter beam 230 incident ondetectors 225 and 226. The degree of focus, then, can be determined bymeasuring the difference between the sum of signals A_(R) and C_(R) andthe center signal E_(R) of detector 225 and the difference between thesum of signals B_(R) and D_(R) and the center signal F_(R) of detector226. Tracking can be monitored by measuring the symmetric placement ofbeams 230 on detectors 225 and 226. A tracking monitor can be providedby monitoring the difference between signals A_(R) and C_(R) of detector225 and the difference between signals B and D of detector 226.Embodiments of OPU 103 are further described in application Ser. No.09/540,657 for “Low Profile Optical Head,” herein incorporated byreference in its entirety.

FIG. 2E shows an effective optical ray diagram for light beam 224traveling from laser 218 (FIG. 2B) to optical media 102 (FIG. 1A) indrive 100. Lens 223 focuses light from laser 218 onto optical media 102at a position x on optical media 102. The distance between lens 223 andthe surface of optical media 102 is designated as d. In some embodimentsof the invention, data is written on the front surface of optical media102. In some embodiments, data can be written on both sides of opticalmedia 102. Further, optical media 102 includes tracks that, in mostembodiments, are formed as a spiral on optical media 102 and in someembodiments can be formed as concentric circles on optical media 102.Tracks 260 can differ between premastered and writeable portions ofoptical media 102. For example, tracks 260 in writeable portions 151 ofoptical media 102 include an addressing wobble while tracks inpremastered portion 150 of optical media 102 do not. Data can be writteneither on the land 261 or in the groove 262. For discussion purposesonly, in this disclosure data is considered to be written on land 261 sothat focus and tracking follow land 261. However, one skilled in the artwill recognize that the invention disclosed here is equally applicableto data written in groove 262.

In premastered portion 150 of optical media 102 (FIG. 1B), data iswritten as pits or bumps so that the apparent reflective property ofreflected beam 230 changes. Although the actual reflectivity of a bumpis the same as the reflectivity elsewhere on the disk, the apparentreflectivity changes because a dark spot over the premastered marks iscreated due to phase differences in light reflected from the bump versuslight reflected from land 261 around in the bump. The phase differenceis sufficient to cause destructive interference, and thus less light iscollected. Another factor in reducing the amount of light detected fromoptical media 102 at a bump includes the additional scattering of lightfrom the bump, causing less light to be collected.

In writeable portion 151 of optical media 102 (FIG. 1B), a film ofamorphous silicon provides a mirrored surface. The amorphous silicon canbe written by heating with a higher powered laser beam to crystallizethe silicon and selectively enhances, because the index of refraction ofthe material is changed, the reflectivity and modifies the phaseproperties of the writeable material in writeable portion 151 of opticalmedia 102.

FIG. 2F shows the reflection of light beam 230 from optical media 102onto detector arrays 225 and 226 of OPU 103. Reflected light beam 230from optical media 102 is collected by lens 223 and focused on detectors225 and 226 in OPU 103. Detector 226 is positioned before the focalpoint of lens 223 while detector 225 is positioned after the focal pointof lens 223. As shown in FIG. 2B, the light beam reflected from opticalmedia 102 is split at surface 213 to be reflected onto each of detectors225 and 226. Detectors 225 and 226 can then be utilized in adifferential manner to provide signals to a servo control that operatesactuators 201 and 206 to maintain optimum tracking and focus positionsof OPU 103.

FIG. 2G shows light beam 230 on optical detectors 225 and 226 when d,the distance between lens 223 and the surface of optical media 102, isat an optimum in-focus position. The light intensity of light beam 230reflected from optical media 102 onto detectors 225 and 226 is evenlydistributed across segments 231, 232, and 233 of detector 225 and acrosssegments 234, 235, and 236 of detector 226. FIG. 2H shows the lightbeams on detectors 225 and 226 when d is lengthened. The beam ondetector 226 gets larger while the beam on detector 225 gets smaller. Asshown in FIG. 2I, the opposite case is true if distance d is shortened.A focus signal on detector 225, then, can be formed by adding signals Aand C and subtracting signal E. In some embodiments, the resultingsignal is normalized by the sum of signals A, C and E. FIG. 2J shows therelationship of quantity A+C−E as a function of d. FIG. 2K shows therelationship of corresponding quantity B+D−F as a function of d. Thedifference between the two functions shown in FIGS. 2J and 2K is shownin FIG. 2L. In FIG. 2L, the focus point can be at the zero-crossing ofthe curve formed by taking the difference between the graphs of FIGS. 2Jand 2K as a function of focus distance d. In the preceding discussion,subscripts are dropped from the detector signals A, C, E, B, D, and F toindicate that the discussion is valid for the analog or digital versionsof these signals.

FIG. 2M shows beam of light 230 on each of detectors 225 and 226 in anon-track situation. As shown in FIG. 2E, light from laser 218 isincident on optical media 102 which has tracks 260 with lands 261 andgrooves 262. The beam is broad enough that interference patterns areformed in the reflected light beam that, as shown in FIG. 2F, isincident on detectors 226 and 225. As shown in FIG. 2M, the interferencepattern forms an intensity pattern with most of the intensity centeredon elements 232 and 235, the center elements of detectors 225 and 226,respectively, where constructive interference from tracks 260 is formed.Lower intensity light, where destructive interference is formed, isincident on outside elements 231 and 233 of detectors 225, 234 and 236of detector 226. If light beam 224 from laser 218 is focused on edges oftracks 260, the interference pattern shifts. FIGS. 2N and 2O showinterference patterns indicative of light at edges of tracks 260. Since,when the light beam is “on-track” the intensity of light in outsideelements 231 and 233 and outside elements 234 and 236 are the same, atracking signal can be formed by the difference in signals A and C and Band D. FIG. 2P shows the normalized value A−C as a function of x aslight beam 224 from laser 218 is moved over the surface of optical media102. FIG. 2Q shows the normalized value of B−D as a function of x. Ineach case, a sinusoidal function is generated where an on-trackcondition is met at zero-crossings. Because detectors 225 and 226 aredifferential in nature, and because the relationship shown in FIG. 2Q isout of phase with that shown in FIG. 2P, an overall tracking errorsignal can be formed by taking the difference between the calculationsshown in FIG. 2P and the calculations shown in FIG. 2Q as an indicationof tracking error. Variation over a complete period of the sine waveshown in FIG. 2Q indicates a full track crossing. In other words, azero-crossing will indicate either land 261 or groove 262 of track 260.The slope of the tracking error signal (TES) at the zero crossing canindicate whether the crossing is through a groove or through a land intrack 260.

Utilizing detectors 225 and 226 in a normalized and differential mannerto form tracking and focus error signals minimizes the sensitivity ofdrive 100 to variations in laser power or to slight differences inreflectivity as optical media 102 is rotated. Variations common to bothdetectors 225 and 226 are canceled in a differential measurement.Further, although best tracking and best focus may occur at zero pointsin the TES or FES signals, these locations may not be optimum for thebest reading or writing of data. Since the purpose of drive 100 is toread and write data to optical media 102, in some embodiments differentoperating points may be made thus allowing drive 100 to switch betweenoptimum servo function and optimum data read function. This factor isfurther discussed below with respect to the TES and FES servoalgorithms.

Further, there can be significant cross-talk between the TES and FESsignals as described above with FIGS. 2A through 2R. FES, as definedabove for each of detectors 225 and 226, will depend on TES as OPU 103passes over tracks on optical media 102. With the observation that thecross-talk intensity changes are concentrated on the outer elements(e.g., elements 231 and 233 of detector 225) and that the sum signal isnot dependent on spot size, so long as the spot stays on detector 225,then FES can be defined such that cross-talk is reduced or eliminated.For example, with detector 225 FES is defined as (A+C−E)/(A+C+E). Sincethe cross-talk in the outer elements (elements 231 and 233) have a largecrosstalk the cross-talk in the central element, element 232, is smallerand out of phase with the cross-talk in the outer elements, thencross-talk can be reduced by defining a new FES, NFES, as FES−SUM, whereSUM is A+C+E. In some embodiments, NFES can be FES−HP(SUM), whereHP(SUM) is a high-pass filtered sum signal with a filter gain chosen toreduce cross-talk. In some embodiments, NFES can be normalized with theSUM signal or with a low-pass filtered SUM signal. In differential mode,i.e. with both detectors 225 and 226, the new FES signal with reducedcross-talk can be defined, as above, by the difference between the FESsignal calculated from detector 225 and the FES signal calculated fromdetector 226.

Embodiments of drive 100 (FIG. 1A) present a multitude of challenges incontrol over conventional optical disk drive systems. A conventionaloptical disk drive system, for example, performs a two-stage trackingoperation by moving the optics and focusing lens radially across thedisk on a track and performs a two-stage focusing operation by moving afocusing lens relative to the disk. Actuators 201 and 206 of actuatorarm 104 provide a single stage of operation that, nonetheless in someembodiments, performs with the same performance as conventional driveswith conventional optical media. Further, conventional optical diskdrive systems are much larger than some embodiments of drive 100. Somemajor differences include the actuator positioning of actuator arm 104,which operates in a rotary fashion around spindle 200 for tracking andwith a flexure action around axis 204 for focus. Further, the speed ofrotation of spindle driver 101 is dependent on the track position ofactuator arm 104. Additionally, the characteristics of signals A_(R),B_(R), C_(R), D_(R), E_(R), and F_(R) received from OPU 103 differ withrespect to whether OPU 103 is positioned over a premastered portion ofoptical media 102 or a writeable portion of optical media 102. Finally,signals A_(R), B_(R), C_(R), D_(R), E_(R), and F_(R) may differ betweena read operation and a write operation.

It may generally be expected that moving to a light-weight structuraldesign from the heavier and bulkier conventional designs, such as isillustrated with actuator arm 104, for example, may reduce many problemsinvolving structural resonances. Typically, mechanical resonances scalewith size so that the resonant frequency increases when the size isdecreased. Further, focus actuation and tracking actuation in actuatorarm 104 are more strongly cross-coupled in actuator arm 104, whereas inconventional designs the focus actuation and tracking actuation is moreorthogonal and therefore more decoupled. Further, since all of theoptics in drive 100 are concentrated at OPU 103, a larger amount ofoptical cross-coupling between tracking and focus measurements can beexperienced. Therefore, servo system 120 has to push the bandwidth ofthe servo system as hard as possible so that no mechanical resonances inactuator arm 104 are excited while not responding erroneously tomechanical and optical cross couplings. Furthermore, due to the loweredbandwidth available in drive 100, nonlinearities in system response canbe more severe. Further, since drive 100 and optical media 102 aresmaller and less structurally exact, variations in operation betweendrives and between various different optical media can complicatecontrol operations on drive 100.

One of the major challenges faced by servo system 120 of control system106, then, includes operating at lower bandwidth with large amounts ofcross coupling and nonlinear system responses, and significant variationin servo characteristics between different optical media and betweendifferent optical drives. Additionally, the performance of drive 100should match or exceed that of conventional CD or DVD drives in terms oftrack densities and data densities. Additionally, drive 100 needs tomaintain compatibility with other similar drives so that optical media102 can be removed from drive 100 and read or written to by anothersimilar drive.

Conventional optical drive servo systems are analog servos. In an analogenvironment, the servo system is limited with the constraints of analogcalculations. Control system 106, however, can include substantially adigital servo system. A digital servo system, such as servo system 120,has a higher capability in executing solutions to problems of systemcontrol. A full servo loop is formed when servo system 120 is coupledwith actuator 104, OPU 103, spin motor 101 and optical media 102, wherethe effects of a control signal generated by servo system 120 isdetected. A full digital servo system is limited only by the designer'sability to write code, the memory storage available in which to storedata and code, and processor capabilities. Embodiments of servo system120, then, can operate in the harsher control environment presented bydisk drive 100 and are capable of higher versatility towards upgradingservo system 120 and for refinement of servo system 120 than inconventional systems.

Drive 100 can also include error recovery procedures. Embodiments ofdrive 100 which have a small form factor can be utilized in portablepackages and are therefore subject to severe mechanical shocks andtemperature changes, all of which affect the ability to extract data(e.g., music data) from optical media 102 reliably or, in some cases,write reliably to optical media 102. Overall error recovery and controlsystem 106 is further discussed in the System Architecture disclosures,while tracking, focus and seek algorithms are discussed below, and inthe Tracking and Focus Servo System disclosures. Further, since drive100, therefore, has tighter tolerances than conventional drives, someembodiments of servo-system 120 include dynamic calibration procedures,which is further described in the Servo System Calibration disclosures.Control of the spin motor 101 is described in the Spin Motor ServoSystem disclosures. The System Architecture disclosures, the Trackingand Focus Servo System disclosures, the Servo System Calibrationdisclosures, and the Spin Motor Servo System disclosures have beenincorporated by reference into this disclosure.

Example Embodiment of an Optical Drive Controller

FIG. 3A shows a block diagram of an embodiment of controller 106according to the present invention. Optical signals are received fromOPU 103 (see FIGS. 2B-2D). As discussed above with FIGS. 2B, 2C and 2D,some embodiments of OPU 103 include two detectors with detector 225including detectors 231, 232, and 233 for providing detector signalsA_(R), E_(R), and C_(R), respectively, and detector 226 having detectors234, 235 and 236 providing detector signals B_(R), F_(R), and D_(R),respectively. Further, some embodiments of OPU 103 include a laser powerdetector 250 mounted to receive reflected light from an annularreflector 252 positioned on periscope 210, as discussed above, andtherefore provides a laser power signal LP_(R) as well.

Detector signals received from OPU 103 are typically current signals.Therefore, the detector signals from OPU 103 are converted to voltagesignals in a preamp 310. Preamp 310 includes a transimpedance amplifier,which converts current signals to voltage signals. Further, preamp 310generates a high frequency (HF) signal based on the detector signalsfrom OPU 103. The HF signal can be utilized as the data signal and isformed by the analog sum of the signals from OPU 103 (signals A_(v),B_(v), C_(v), D_(v), E_(v) and F_(v) in FIG. 3A).

FIG. 3B shows a block diagram of an embodiment of preamp 310. Preamp 310includes an array of transimpedance amplifiers, amplifiers 311, 312,313, 314, 315, 316 and 317 in FIG. 3B. Amplifier 311 receives the laserpower signal LP_(R) from OPU 103 and amplifiers 312 through 317 receivesignals A_(R) through F_(R), respectively, from OPU 103. In general,preamp 310 can receive any number of detector signals from OPU 103. Insome embodiments, each of signals A_(R) through F_(R) and laser powerLP_(R) are current signals from detectors 225, 226 and 250 of OPU 103.Amplifiers 311 through 317 output voltage signals LP_(v), A_(v), B_(v),C_(v), D_(v), E_(v), and F_(v), respectively. The gain of each ofamplifiers 311 through 317, G1 through G7, can be set by gain conversion318. Gain conversion 318 can receive a W/R gain switch that indicates aread or a write condition and can adjust the gains G1 through G7 ofamplifiers 311 through 317 accordingly. In some embodiments, gainconversion 318 receives gain selects for each of gains G1 through G7 anda forward sensor FWD sensor. In some embodiments, gains G1 and G2 arethe same and gains G3 through G6 are the same. In some embodiments,gains G3 through G6 are approximately ½ of gains G1 and G2.

Since the laser power required for a write operation is much higher thanthe laser power required for a read operation, the gains G1 through G7can be set high for a read operation and can be lowered for a writeoperation. In some embodiments, gain conversion 318 outputs one of anumber (e.g., two) of preset gains for each of gains G1 through G7 inresponse to the W/R gain switch setting. Summer 319 receives each of thesignals A_(v), B_(v), C_(v), D_(v), E_(v), and F_(v) from amplifiers 312through 317, respectively, and outputs a differential HF signal. In someembodiments, the differential HF signal is the analog sum of signalsA_(v), Bv, C_(v), D_(v), E_(v), and F_(v)The differential HF signalindicates the total light returned from optical medium 102 (see FIG. 1)and therefore includes, in a read operation, the actual data read fromoptical medium 102.

In some embodiments, preamplifier 308 can include summers 331 through336, which receives the output signals from amplifiers 312 through 317,respectively, and offsets the output values from amplifiers 312 through317, respectively, by reference voltages VREF6, VREF5, VRD4, VRD3, VRD2,and VRD1, respectively. In some embodiments VRD1 through VRD4 are thesame and VREF5 and VREF6 are the same. The input signals to differentialsummer 319, then, are the output signals from adders 331 through 336 andthe output signal from amplifier 311.

As shown in FIG. 3A, the voltage signals LP_(v), A_(v), B_(v), C_(v),D_(v), E_(v), F_(v), and HF from preamp 310 are input signals to controlchip 350. Control chip 350 can be a digital and analog signal processorchip which digitally performs operations on the input signals A_(v),B_(v), C_(v), D_(v), E_(v), F_(v), HF, and LP_(v) to control theactuators of actuator arm 104 (FIG. 1), the laser power of laser 218(FIG. 2B), and the motor speed of spindle motor 101 (FIG. 1). Control350 also operates on the HF signal to obtain read data and communicatedata and instructions with a host (not shown). In some embodiments,control 350 can be a ST Microelectronics 34-00003-03.

The laser power signal LP_(v) is further input to laser servo 105 alongwith a W/R command, indicating a read or a write operation. In someembodiments, laser servo 105 is an analog servo loop that controls thepower output of laser 218 of OPU 103. In some embodiments, the laserpower can also be included in a digital servo loop controlled by controlchip 350. The laser power of laser 218 is high for a write operation andlow for a read operation. Laser servo 105, then, holds the power oflaser 218 to a high power of low power in response to the laser W/Rpower control signal from control chip 350. Analog servo systems forutilization as laser servo 105 are well known to one skilled in the art.In some embodiments, laser servo 105 can also be a digital servo system.

Control chip 350 is further coupled with data buffer memory 320 forbuffering data to or from the host and program memory 330. Programmemory 330 holds program code for, among other functions, performing theservo functions for controlling focus and tracking functions, laserpower, and motor speed. Data read through OPU 103 can be buffered intodata buffer memory 320, which assists in power savings and allows moretime for error recovery if drive 100 suffers a mechanical shock or otherdisturbing event. In some embodiments, control chip 350 activatesmechanical components 107 of drive 100 when data buffer 320 is depletedand deactivates mechanical portions 107 when buffer 320 is filled. Servosystem 120, then, needs only to be active while mechanical portions 107are active.

In some embodiments, control chip 350 is a low power device thatoperates at small currents. Therefore, control voltages for controllingfocus and tracking actuators (through coils 206 and 201, respectively)are input to power driver 340. Power driver 340 outputs the currentrequired to affect the focus and tracking functions of actuator arm 104through focus actuator 206 and tracking actuator 201. In someembodiments, as described above, focus actuator 206 and trackingactuator 201 are voice coil motors mounted on actuator arm 104 so thattracking actuator 201 moves OPU 103 over tracks of optical media 102 andfocus actuator 206 flexes actuator arm 104 to affect the distancebetween OPU 103 and optical media 102.

Driver 340 can also provide current to drive spindle motor 101. Spindlemotor 101 provides sensor data to a servo system and can also beresponsive to the tracking position of OPU 103 so that the speed ofspindle motor 101 is related to the track. In some embodiments, the datarate is held constant by controlling the speed of spindle motor 101 asOPU 103 tracks across optical media 102. A servo system for controllingspindle motor 101 is further described in the Spin Motor Servo Systemdisclosures.

Further, power drivers 340 can also control a cartridge eject motor 360and latch solenoid 370 in response to commands from control chip 350.Cartridge eject motor 360 mounts and dismounts optical media 102 ontospindle motor 101. Latch solenoid 370 provides a secured latch so thatthe OPU 103 does not contact optical media 102 during non-operationalshock conditions.

Finally, system 300 can include power monitor 380 and voltage regulators390. Power monitor 380 provides information about the power source tocontrol chip 350. Control chip 350, for example, can be reset by powermonitor 380 if there is a power interruption. Voltage regulators 390, inresponse to an on/off indication from control chip 350, provides powerto drive laser 218, as well as control chip 350 and pre-amp 310. Spindlemotor 101, actuators 206 and 201, cartridge eject motor 360, and latchsolenoid 370 can be powered directly from the input voltage.

FIG. 4 shows an embodiment of control chip 350 of control system 300.The embodiment of control chip 350 shown in FIG. 4 includes amicroprocessor 432 and a digital signal processor (DSP) 416. Since DSP416 operates much faster, but has lower overall capabilities (e.g., codeand data storage space), than microprocessor 432, in some embodimentsreal time digital servo system algorithms can be executed on DSP 416while other control functions and calibration algorithms can be executedon microprocessor 432. A control structure for embodiments of controlchip 350, and interactions between DSP 416 and microprocessor 432, arefurther discussed in the System Architecture disclosures.

Control chip 350 receives voltage signals A_(v), E_(v), C_(v), B_(v),F_(v), D_(v), HF, and LP_(v) from preamp 310 (see FIG. 3A). SignalsA_(v), E_(v), C_(v), B_(v), F_(v), and D_(v) are input into offsetblocks 402-1 through 402-6, respectively. Offset blocks 402-1 through402-6 provide a variable offset for each of input signals A_(v), E_(v),C_(v), B_(v), F_(v), and D_(v). The value of the offset is variable andcan be set by a calibration routine executed in microprocessor 432 orDSP 416, which is further described below.

In some embodiments, the offset values can be set so that when the powerof laser 218 is off the output signal from each of offsets 402-1 through402-6 is zero, i.e. a dark-current calibration. In some embodiments, theeffects of light scattering in OPU 103 may also be deducted in offset402-1 through 402-6.

The signals output from offsets 402-1 through 402-6 are input tovariable gain amplifiers 404-1 through 404-6, respectively. Again, thegains of each of variable gain amplifiers 404-1 through 404-6 are set bya calibration routine executed in microprocessor 432 or DSP 416, asfurther described below. In some embodiments, the gains of amplifiers404-1 through 404-6 can be set so that the dynamic range ofanalog-to-digital converters 410-1 and 410-2 are substantially fullyutilized in order to reduce quantization error.

The offsets and gains of offsets 402-1 through 402-6 and 404-1 through404-6, respectively, may be different for each of signals A_(v), E_(v),C_(v), B_(v), F_(v), and D_(v). Further, the gains and offsets may bedifferent for read operations and write operations and may be differentfor pre-mastered verses writeable portions of optical media 102.Further, the offsets and gains may vary as a function of trackingposition on optical media 102 (in addition to simply varying betweenpremastered or writeable regions). Some factors which may further leadto different offset and gain settings include light scattering ontodetectors, detector variations, detector drift, or any other factorwhich would cause the output signal from the detectors of OPU 103 tovary from ideal output signals. Various calibration and feedbackroutines can be operated in microprocessor 432 and DSP 416 to maintainefficient values of each of the offset and gain values of offsets 402-1through 402-6 and amplifiers 404-1 through 404-6, respectively, overvarious regions of optical media 102, as is further discussed below.

Therefore, in some embodiments the offset and gain values of offsets402-1 through 402-6 and amplifiers 404-1 through 404-6 can be varied bymicroprocessor 432 and DSP 416 as OPU 103 is positionally moved overoptical media 102. Additionally, in some embodiments microprocessor 432and DSP 416 monitor the offset and gain values of offset 402-1 through402-6 and amplifiers 404-1 through 404-6 in order to dynamicallymaintain optimum values for the offset and gain values as a function ofOPU 103 position over optical media 102. In some embodiments, offset andgain values are set in a calibration algorithm. In some embodiments, theoffset values of offsets 402-1 through 402-6 are determined such thatthe dynamic range of the respective input signals are centered at zero.Further, the gains of amplifiers 404-1 through 404-6 are set to fill thedynamic range of analog-to-digital converters 410-1 and 410-2 in orderto reduce quantization error. In some embodiments, the gains ofamplifiers 404-1 through 404-6 can be modified in error recoveryroutines. See the System Architecture disclosures. In some embodiments,the gains of amplifiers 404-1 through 404-6 can be optimized throughcontinuous performance monitoring. See the Servo System Calibrationdisclosures.

The output signals from variable gain amplifiers 404-1 through 404-6 areinput to anti-aliasing filters 406-1 through 406-6, respectively.Anti-aliasing filters 406-1 through 406-6 are low-pass filters designedto prevent aliasing. In some embodiments, the output signals from eachof anti-aliasing filters 406-1 through 406-5 are input toanalog-to-digital converters. In other embodiments, a limited number ofanalog-to-digital converters are utilized. In the embodiment shown inFIG. 4, the output signals from anti-aliasing filters 406-1 through406-5 are input to multiplexers 408-1 and 408-2. The output signals fromanti-aliasing filters 406-1 through 406-3 are input to multiplexer 408-1and the output signals from anti-aliasing filters 406-4 through 406-6are input to multiplexer 408-2.

The HF signal from preamp 310 (see FIG. 3A) can be input to equalizer418. Equalizer 418 equalizes the HF signal by performing a transformfunction that corrects systematic errors in detecting and processingdata read from optical media 102. In some embodiments, equalizer 418operates as a band-pass filter. The output signal from equalizer 418 isinput to amplifier 420. The output signal from amplifier 420 can beinput as a fourth input to multiplexer 408-1.

The laser power signal LP_(v) can be input to multiplexer 436 whereLP_(v) can be multiplexed with other signals that may requiredigitization. The output signal from multiplexer 436 can then be inputas a fourth input to multiplexer 408-2. One skilled in the art willrecognize that if no other signals are being digitally monitored,multiplexer 436 can be omitted. Further, one skilled in the art willrecognize that any number of analog-to-digital converters can beutilized and any number of signals can be multiplexed to utilize theavailable number of analog-to-digital converters. The particularembodiment shown here is exemplary only.

The output signal from multiplexer 408-1 is input to analog-to-digitalconverter 410-1. The output signal from multiplexer 408-2 is input toanalog-to-digital converter 410-2. Analog-to-digital converters 410-1and 410-2 can each include registers 478 for the storage of digitizedvalues. ADC 410-1 includes registers 478-1 through 478-4 and ADC 410-2includes registers 478-5 through 478-8. Further, multiplexers 408-1 and408-2 and ADC 410-1 and 410-2 are coupled to a clock 476 whichdetermines which signals from multiplexers 408-1 and 408-2 are currentlybeing digitized and, therefore, in which of register 478-1 through 478-4the result of that digitization should be stored. In some embodiments,analog-to-digital converters 410-1 and 410-2 can be, for example, 10 bitconverters sampling at a rate of about 26 Mhz, with each sample beingtaken from a different input of multiplexers 408-1 and 408-2,respectively. In some embodiments ADC 410-1 and 410-2 can sample theoutput signals from anti-aliasing filters 406-1 through 406-6 at ahigher rate than other signals, for example the LP_(v) signal or theoutput signal from gain 420. In some embodiments, for example, ADC 410-1and 410-2 may sample each of the output signals from anti-aliasingfilters 406-1 through 406-6 at an effective sampling rate of about 6.6MHz.

The digitized signals from analog-to-digital converts 410-1 and 410-2,then, are the digitized and equalized HF signal HF_(d), the digitizedlaser power signal LP_(d), and digitized detector signals A_(d), E_(d),C_(d), B_(d), F_(d), and D_(d). Digitized laser power signal LP_(d) isinput to DSP 416 and can be utilized in a digital servo loop forcontrolling laser power or in determination of gain and offset valuesfor various components. Alternatively, DSP 416 or microprocessor 432 canmonitor LP_(d) to determine error conditions.

The digitized HF signal HF_(d) can be input to focus OK (FOK) 412, whichoutputs a signal to DSP 416 and microprocessor 432 indicating whetherfocus is within a useful range. Detectors 225 and 226 are sized suchthat, when OPU 103 is seriously out of focus, light is lost offdetectors 225 and 226. Therefore, FOK 412 determines if the totalintensity of light on detectors 225 and 226 is above a FOK thresholdvalue indicating a near in-focus condition. In some embodiments, thisfunction can also be executed in software rather than hardware. Further,the FOK threshold value can be fixed or can be the result of acalibration algorithm. In some embodiments, the FOK threshold value canbe dependent upon the type of media on optical media 102 that OPU 103 iscurrently over.

Digitized detector signals A_(d), E_(d), C_(d), B_(d), F_(d), and D_(d)are input to decimation filters 414-1 through 414-6, respectively.Decimation filters 414-1 through 414-6 are variable filters whichdown-sample the digitized detector signals A_(d), E_(d), C_(d), B_(d),F_(d), and D_(d) to output signals A_(f), E_(f), C_(f), B_(f), F_(f),and D_(f), which are input to DSP 416. In some embodiments, for example,each of signals A_(d), E_(d), C_(d), B_(d), F_(d), and D_(d) haseffectively been sampled at 6.6 MHz by ADC 410-1 and 410-2. Decimationfilters 414-1 through 414-6 can then down-sample to output signalsA_(f), E_(f), C_(f), B_(f), F_(f), and D_(f) at, for example, about 70kHz. Embodiments of decimation filters 414-1 through 414-6 candown-sample to any sampling rate, for example from about 26 kHz to about6.6 MHz.

The effects of down-sampling in decimation filters 414-1 through 414-6include an averaging over several samples of each of signals A_(d),E_(d), C_(d), B_(d), F_(d), and D_(d). This averaging provides alow-pass filtering function and provides higher accuracy for signalsA_(f), E_(f), C_(f), B_(f), F_(f), and D_(f) which are actually read byDSP 416 and utilized in further calculations. In some embodiments, theaccuracy is effectively increased to 13 bits from the 10 bit outputsignals from ADC 410-1 and 410-2.

Further, although the data signals included in the HF signal can be athigh frequency (e.g., several MHz), the servo information is at muchlower frequencies. In some embodiments, the mechanical actuators 206 and201 of actuator arm 104 can respond to changes in the hundreds of hertzrange yielding servo data in the 10s of kilohertz range, rather than inthe Megahertz ranges of optical data. Further, mechanical resonances ofactuator arm 104 can occur in the 10's of kilohertz range. Therefore,down-sampling effectively filters out the high frequency portion of thespectrum that is not of interest to servo feedback systems. Further, amuch cleaner and more accurate set of digital servo signals A_(f),E_(f), C_(f), B_(f), F_(f), and D_(f) are obtained by the averagingperformed in decimation filters 414-1 through 414-6, respectively. Insome embodiments, decimation filters 414-1 through 414-6 can beprogrammed by microprocessor 432 or DSP 416 to set the output frequency,filtering characteristics, and sampling rates.

In particular, a tracking wobble signal at about 125 KHz in the track onwriteable portions 151 of optical media 102 results from a slightmodulation in the physical track in that region. This wobble is filteredout of signals A_(f), E_(f), C_(f), B_(f), F_(f), and D_(f) by filteringprovided in decimation filters 414-1 through 414-6. Actuator arm 104cannot respond to control efforts in this frequency range. Similarly, astabilizing frequency on laser power at 500 MHz, from modulator 219 (seeFIG. 2B), is filtered out of signals A_(f), E_(f), C_(f), B_(f), F_(f),and D_(f) by filtering provided in decimation filters 414-1 through414-6. For servo purposes, only the lower frequency region of thesignals are important. Then, the signals A_(f), E_(f), C_(f), B_(f),F_(f), and D_(f) only include sensor noise and real disturbances thatcan be followed by a servo system operating on, for example, actuatorarm 104. Those disturbances can include physical variations due tostamping errors in the mastering process, since tracks will not beperfectly laid. In addition, spindle motor 101 may provide some errorsthrough bearings that cause vibration. Additionally, optical media 102may not be flat. Tracking and focus servo functions, as well as theservo systems tracking laser power and the rotational speed of spindlemotor 101, can follow these errors. Further, it is important that thespectral response of a servo system be responsive to the frequency rangeof the errors that are being tracked. If not, then the servo system maymake the tracking and focus environments worse. Further, embodiments ofdrive 100 operate in extremes of physical abuse and environmentalconditions that may alter the resonant frequency characteristics andresponse characteristics of spindle motor 101, optical media 102, andactuator arm 104 during operation in the short term or during thelifetime of drive 100 or optical media 102. A servo system according tothe present invention should be insensitive to these changingconditions.

The digital output signals A_(d), E_(d), C_(d), B_(d), F_(d), and D_(d)are further input to summer 438. Summer 438 can be a programmable summerso that a sum of particular combinations of inputs A_(d), E_(d), C_(d),B_(d), F_(d), and D_(d) can be utilized. Summer 438 sums a selected setof signals A_(d), E_(d), C_(d), B_(d), F_(d), and D_(d) to form alow-bandwidth digitized version of the HF signal. The output signal fromsummer 438 is multiplexed in multiplexer 441 and multiplexer 443 withthe digitized HF signal HF_(d) output from ADC 410-1. A HF select signalinput to each of multiplexer 441 and 443 selects which of HF_(d) or theoutput signal from summer 438 are chosen as the output signal frommultiplexer 441 and 443. The output signal from multiplexer 441 is inputto disturbance detector 440. Disturbance detector 440 detects defects onmedia 102 by monitoring the data signal represented by HF_(d) or theoutput from summer 438 and alerts DSP 416 of a defect. A defect caninclude a scratch or speck of dust on optical media 102. Results ofdefects manifest themselves as sharp spikes in the input signal. In someembodiments, disturbance detector 440 can include a low pass filter. Theinput signal to disturbance detector 440 is low pass filtered and thefiltered signal is compared with the unfiltered input signal. If thedifference exceeds a pre-set defect threshold signal, then a defect flagis set. The defect flag can be input to DSP 416 or microprocessor 432.

The output signal from multiplexer 443 is also input to mirror detector442. Mirror detector 442 provides a signal similar to the TES , but 90degrees out of phase. DSP 416 receives the mirror signal and, incombination with the TES calculated within DSP 416, can determinedirection of motion while track seeking. The TES is a sine wave thatindicates a track jump over one period of the wave. If a tracking servosystem attempts to track at the zero-crossing with an improper slope,the servo system will simply move actuator arm 104 away from thatzero-crossing. The mirror signal can be utilized to indicate if themotion is in the proper direction.

Additionally, signals A_(d) and C_(d) are received in summer 444, whichcalculates the value A_(d)-C_(d). Further, signals B_(d) and D_(d) areinput to summer 446 which calculates the value B_(d)−D_(d). The outputsignals from summer 444 and summer 446 are input to summer 448, whichtakes the difference between them forming a version of tracking errorsignal, TES, from the digitized detector output signals. The outputsignal from summer 448 is input to a bandpass filter 450. The outputsignal from bandpass filter 450 is PushPullBP. The output signal fromsummer 448 is further input to a lowpass filter 452. The output signalfrom lowpass filter 452 is input to track crossing detector 454 whichdetermines when the TES calculated by summer 448 indicates that OPU 103has crossed a track on optical media 102. The output signal from trackcrossing detector 454 is the TZC signal and is input to DSP 416.

The low-pass filtered TES is a sine wave as a function of position ofOPU 103 over optical media 102. (See, e.g., FIG. 2R). A one-periodchange in TES indicates a track crossing. Then, in some embodimentstrack crossing detector 454 can output a TZC pulse whenever the TEScrosses zero (which results in two pulses per track crossing). In someembodiments, track crossing detector 454 can generate a pulse whenever azero crossing having the proper slope in the TES curve is detected.

The signal PushPullBP can be input to Wobble/PreMark detector 428. Insome embodiments, in the writeable portion of optical media 102 thetracks have a predetermined wobble, resulting from an intentionalmodulation in track position, which has a distinct frequency. In someembodiments, the wobble frequency of PushPullBP is in the 100 kHz range(in some embodiments around 125 kHz) and therefore, with decimationfilters 414-1 through 414-6 operating as a low-pass filter at around 70kHz, is filtered out of signals A_(f), E_(f), C_(f), B_(f), F_(f), andD_(f). Bandpass filter 450 can be set to pass TES signals of thatfrequency so that detector 428 detects the wobble in the track.

The frequency of wobble in the track from detector 428 is indicative ofthe rotational speed of spindle driver 101. Further, a spindle speedindication from spindle motor 101 itself can be directly input tomicroprocessor 432 and DSP 416. Further, the signal from gain 420 can beinput to slicer 422, DPLL 424, and Sync Mark Detector 426 to provide athird indication of the speed of spindle motor 101. Slicer 422determines a digital output in response to the output signal fromequalizer 418 and amplifier 420. Slicer 422 simply indicates a highstate for an input signal above a threshold value and a low state for aninput signal below the threshold. DPLL 424 is a digital phase-lockedloop, which basically servos a clock to the read back signal so thatsync marks on the tracks can be detected. Sync mark detector 426, then,outputs a signal related to the period between detected sync marks,which indicates the rotational speed of spindle driver 101.

Each of these speed indications can be input to multiplexer 430, whoseoutput is input to microprocessor 432 as the signal indicating therotational speed of spindle motor 101. Microprocessor 432 can choosethrough a select signal to multiplexer 430 which of these rotationalspeed measurements to use in a digital servo loop for controlling therotational speed of spindle driver 101.

Microprocessor 432 and DSP 416 output control efforts to drivers thataffect the operation of drive 100 in response to the previouslydiscussed signals from actuator arm 104 and spindle driver 101. Acontrol effort from microprocessor 432 is output to spin control 456 toprovide a spin control signal to driver 340 (see FIG. 3A) forcontrolling spindle driver 101. A digital servo system executed onmicroprocessor 432 or DSP 416 is further discussed in the Spin MotorServo System disclosures. In some embodiments, as is further discussedbelow, microprocessor 432 outputs a coarse tracking control effort toserial interface 458.

In embodiments of drive 100 with a digital servo loop for controllinglaser power, a signal from microprocessor 432 or DSP 416 is input to alaser control digital to analog converter 460 to provide a controleffort signal to the laser driver of laser servo 105 (see FIG. 3A). Afocus control signal can be output from either microprocessor 432 or DSP416 to a focus digital to analog converter 464 to provide a focuscontrol signal to power driver 340 (see FIG. 3A). A tracking controlsignal, which in some embodiments can be a fine tracking control effort,can be output from either microprocessor 432 or DSP 416 to a trackingdigital to analog converter 468 to provide a tracking control signal topower drivers 340. A diagnostic digital to analog converter 466 andother diagnostic functions, such as analog test bus 470, digital testbus 472, and diagnostic PWM's 474, may also be included. Further areference voltage generator 462 may be included to provide a referencevoltage to digital-to-analog converters 460, 464, 466, and 468.

Microprocessor 432 and DSP 416 can communicate through direct connectionor through mailboxes 434. In some embodiments, DSP 416 operates underinstructions from microprocessor 432. DSP 416, for example, may be setto perform tracking and focus servo functions while microprocessor 432provides oversight and data transfer to a host computer or to buffermemory 320. Further, microprocessor 432 may provide error recovery andother functions. Embodiments of control architectures are furtherdiscussed in the System Architecture disclosures. DSP 416, in someembodiments, handles only tracking and focus servo systems whilemicroprocessor 432 handles all higher order functions, including errorrecovery, user interface, track and focus servo-loop closings, datatransport between optical media 102 and buffer memory 320, and datatransfer between buffer memory 320 and a host, read and writeoperations, and operational calibration functions (including settingoffset and gain values for offset 402-1 through 402-6 and amplifiers404-1 through 404-6 and operational parameters for decimation filters414-1 through 414-6).

Tracking and Focus Servo Algorithms

FIGS. 5A and 5B together show a block diagram of an embodiment oftracking, focus and seek algorithms 500. Algorithms 500 shown in FIGS.5A and 5B can be, for example, primarily executed on DSP 416 of FIG. 4.In some embodiments, real-time tracking and focus algorithms areexecuted on DSP 416 whereas other functions, including calibration andhigh-level algorithm supervision, are executed on microprocessor 432. Insome embodiments, microprocessor 432 can also manage which algorithmsare executed on DSP 416. Algorithm 500 includes a focus servo algorithm501 and a tracking algorithm 502. Further algorithms include amulti-track seek algorithm 557 and a one-track jump algorithm 559.

Focus servo algorithm 501, as shown in FIGS. 5A and 5B, includes, whenfully closed, summer 506, offset summer 507, FES gain 509, inversenon-linearity correction 511, cross-coupling summer 513, FES sampleintegrity test 515, low frequency integrator 516, phase lead 518, notchfilter 519, focus close summer 521, loop gain 524, and feed-forwardsummer 533. Similarly, tracking servo loop 502, when fully closed,includes summer 540, offset summer 541, TES gain 543, TES inversenon-linearity correction 546, TES sample integrity test 548, lowfrequency filter 549, phase lead 550, notch filters 551 and 553, andloop gain amplifier 564.

Further, algorithm 500 includes detector offset calibration 584 anddetector gain calibration 583. Along with other calibration proceduresshown in algorithm 500, these calibrations are discussed further below.

As shown in block 503, digitized and filtered signals A_(f), E_(f),C_(f), B_(f), F_(f), and D_(f) from decimation filters 414-1 through414-6 as shown in FIG. 4. For purposes of discussion, signals A_(f),E_(f), C_(f), B_(f), F_(f), and D_(f) have been relabeled in subsequentFigures to be A, E, C, B, F, and D, respectively. Block 504 receivessignals A, C, and E and calculates an FES₁ signal asFES ₁=(A+C−E)/(A+C+E),as was previously discussed with FIG. 2J with the analog versions ofsignals A, C, and E. Block 505 receives signals B, D, and F andcalculates an FES₂ signal according toFES ₂=(B+D−F)/(B+D+F),as was previously discussed with FIG. 2K with the analog versions ofsignals B, D, and F. Summer 506 calculates the differential FES signalaccording toFES=FES ₁ −FES ₂.As was previously discussed, FIG. 2L shows the FES signal as a functionof distance between OPU 103 and optical media 102. As previouslydiscussed, in some embodiments further processing can be performed onTES and FES signals, for example to reduce cross-talk.

The FES signal is input to offset adder 507, which adds an FES offsetfrom offset calibration 508. The best position on the FES curve (seeFIG. 2L) around which a servo system should operate can be different forthe servo system than it is for read or write operations. In otherwords, optimum read operations may occur around a position on the FEScurve that differs from the optimum position utilized for best servooperation. FES offset calibration 508, which inputs the peak-to-peaktracking error signal TES P-P and a data jitter value and outputs an FESoffset value, is further discussed below.

The output signal from offset adder 507 is input to FES Gain 509. Thegain of FES gain 509 is determined by FES gain calibration 510. The gainof FES gain 509 is such that the output value of gain 509 corresponds toparticular amounts of focus displacement at focus actuator 206. Fixingthe correlation of the magnitude of the output signal from gain 509 withparticular physical displacements of OPU 103 allows the setting ofthresholds that determine whether or not focus loop 501 is sufficientlyclosed to transfer data. Although discussed further below, FES gaincalibration 510 can determine an appropriate value of the gain for FESgain 509 by varying the distance between OPU 103 and optical media 102and monitoring the peak-to-peak value of the resulting FES signal. Insome embodiments, the gain of FES gain 509 can be fixed.

As a result of the calibrated gain of FES gain 509, the FES signaloutput from FES gain 509 can have a set peak-to-peak value. Between thepeaks of the amplified FES signal from FES gain 509 is a near linearregion of operation. Focus servo algorithm 501 operates in this regionunless a shock sufficient to knock focus out of the linear region isexperienced. It is beneficial if, between separate drives and betweendifferent optical media 102 on drive 100, along with any differences indetectors and actuator response between drives, that the FES output fromFES gain 509 be normalized. This allows for threshold values independentof particular drive or particular optical media to be set based on theamplified FES to determine ability to read or write to optical media102. In some embodiments, for example, the peak-to-peak motion of OPU103 relative to optical media 102 may correspond to about a 10 μmmovement.

However, although the amplified FES output from FES gain 509 can benormalized to a particular peak-to-peak value corresponding toparticular displacements of OPU 103 relative to optical media 102, theamplified FES output can be non-linear between those peaks. FES inversenon-linearity 511 operates to remove the potentially destabilizingeffects of non-linearity of the amplified FES. In some embodiments,calibration 512 may create a table of gains related to the slope of theFES as a function of the FES offset value. In that case, if a shockoccurs and the servo is on a different offset value of the FES curve,then FES inverse non-linearity 511 can obtain a linearizing gain valuefrom the table of gains. In that fashion, FES inverse non-linearity 511can help quickly react to a shock to recover focus. In some embodiments,the FES curve can be recorded and the gain of FES non-linearity 511 canbe set according to the recorded FES curve. In either case, the gainsetting of inverse non-linearity 511 is set depending on the FES offsetvoltage, which determines the point on the FES curve about which servosystem 501 is operating.

The output signal from FES inverse non-linearity 511 is input tocoupling summer 513. An estimate of the optical cross-coupling with acorresponding TES signal is subtracted from the FES at summer 513. Theestimated correction is determined by Tes-to-Fes Cross-Coupling Gain514. TES-to-FES cross-coupling gain 514 may, in some embodiments,determine the amount of TES to subtract in summer 513 from a ratioproduced by TES-to-FES Cross Talk Gain Calibration 579. As discussedfurther below, calibration 579 can insert a small test component (e.g.,a sine wave) to the tracking control effort signal and measure theeffects on the FES signal at the input of summer 513 in order todetermine the ratio used in cross-coupling gain 514.

Therefore, a certain percentage of the TES signal is subtracted from theFES signal in summer 513. In some embodiments, the particular percentage(indicated by the gain of gain block 514) can be fixed. In someembodiments, a TES-to-FES cross-talk gain calibration 579 determines thegain of gain block 514. Cross-talk gain calibration 579 is furtherdiscussed below. In some embodiments, the gain of gain block 514 can bechanged depending upon the type of media, e.g. writeable or premastered,that OPU 103 is currently over.

The output signal from cross-talk summer 513 is input to FES sampleintegrity test 515. Sharp peaks may occur in the FES signal as a resultof many factors, including defects in optical media 102, dust, andmechanical shocks. These signals occur as a dramatic change from thetypical FES signal that has been observed at integrity test 515. In someembodiments, signals of this type may be on the order of 10 to 500microseconds in duration. In many instances, the resulting FES signalmay indicate an apparent acceleration of actuator arm 104 that isphysically impossible. It would be detrimental to overall operation ofdrive 100 for focus servo algorithm 501 to respond to such sporadicinputs since, if there is a response by focus servo algorithm 501,recovery to normal operation may take a considerable amount of time.Therefore, integrity test 515 attempts to detect such signals in the FESsignal and cause focus servo algorithm 501 to ignore it by filtering thesignal out.

Integrity test 515 inputs a defect signal, which can be the defectsignal output from disturbance detector 440 shown in FIG. 4.Essentially, upon receiving a defect signal, integrity test 515 createsa low-pass filtered version of the FES signal to substitute for thedefective FES signal. In some embodiments, a defect flag can be set eachtime this occurs so that error recovery can be initiated if too manydefects, resulting in filtered FES signals, are experienced. Use of thelow-pass filtered FES signal over a long period of time can causephase-margin problems in focus servo algorithm 501, which can affect thestability of drive 100.

In some embodiments, sample integrity test 515 may low-pass filter FESsignal at its input and subtract the filtered FES signal from thereceived input FES signal. If a peak in the difference signal exceeds athreshold value, then the low-pass filtered FES signal is output fromintegrity test 515 instead of the input FES signal and a defect flag isset or a defect counter is incremented. The occurrence of too manydefects in too short a time can be communicated to an error recoveryalgorithm. See the System Architecture Disclosures.

In some embodiments, the change in the FES signal between adjacentcycles can be monitored. If the change, measured by the differencebetween the FES signal in the current cycle and the previous cycle, isgreater than a threshold value, then the low-pass filtered FES signal isoutput from integrity test 515 instead of the input FES signal and adefect flag can be set and the defect counter incremented.

In some embodiments, FES sample integrity test 515 may be disabled.Disabling FES sample integrity test 515, in some embodiments, may occurduring focus acquisition so that focus servo algorithm 501 can betterrespond to transient effects. In some embodiments, FES sample integritytest 515 may be disabled during multi-track seek algorithm 557 andduring one-track jump algorithm 559. In some embodiments, FES sampleintegrity test 515 may be disabled while track following during a readto write transition.

The output signal from FES sample integrity test 515 is input to TES OKdetector 517. If a low pass filtered (e.g., 200 Hz 2^(nd) order lowpass) version of the absolute value of the FES signal FES′ output fromintegrity test 515 exceeds a TES OK threshold value, then a trackingerror signal TES can not be trusted. In reality, if the FES signaldeviates significantly from its best focus value, then the TES signalcan become small. A small TES signal indicates to tracking servoalgorithm 502 that tracking is good, which is not the case. Instead,focus has deviated so that tracking is no longer reliable. Under theseconditions, an error recovery algorithm can be initiated. See the SystemArchitecture Disclosures.

In some embodiments of the invention, the FES signal FES′ is input toseek notch filter 590. Seek notch filter 590 is adjusted to filter outsignals at the track crossing frequency when a multi-track seekoperation is being performed. Even though there is a TES-FEScross-coupling correction at summer 513, not all of the TES signal willbe filtered out of the FES signal, especially during a multi-track seekoperation. Therefore, notch filter 590 can be enabled during amulti-track seek operation in order to help filter more of the TES-FEScross coupling from the FES signal. When not enabled, notch filter 590does not filter and the output signal from filter 590 matches the inputsignal to filter 590.

The FES signal output from notch filter 590 can be input to lowfrequency integrator 516. The low frequency integrator provides furthergain at low frequencies as opposed to high frequencies. Since theresponses to which focus actuator 206 should respond, as discussedabove, occur at low frequencies, there is a large incentive in focusservo loop 501 to increase the gain at low frequencies and placeemphasis on the servo response at those frequencies. In order to furtheremphasis the low frequencies, in some embodiments low frequencyintegrator 516 can be a 2^(nd) Order low frequency integrator.Integrator 516 provides additional error rejection capability for lowfrequency disturbances such as DC bias, external shock and vibration. Anexample transfer function for low frequency integrator 516 is shown inFIG. 5C. Low frequency integrator 516, for example, can be particularlysensitive to frequencies less than about 100 Hz in order to boost servoresponse to frequencies less than 100 Hz.

The output signal from integrator 516 is input to phase lead 518. Phaselead 518 provides phase margin or damping to the system for improvedstability and transient response. In some embodiments, for example,phase lead 518 can be sensitive to frequencies greater than about 500Hz. Again, in some embodiments of the invention, phase lead 518 can be asecond order phase lead. Further, in some embodiments integrator 516 canbe disabled during focus acquisition in order to allow focus servosystem algorithm 501 to better respond to transient effects during afocus acquisition procedure. An example transfer function for phase lead518 is shown in FIG. 5D.

In some embodiments, low frequency integrator 516 and phase leadcompensation 518 are accomplished with second order filters instead offirst order filters. A second order low frequency integrator providesmore low frequency gain, providing better error rejection, than a firstorder integrator. Additionally, a second order phase lead compensatorprovides increased phase advance or phase margin at the servo open loopbandwidth than that of a first order phase lead compensator. The secondorder phase lead compensator also causes less high frequencyamplification than that of a first order phase lead for the same amountof phase advance at the crossover.

The output signal from phase lead 518 can be input to a notch filter519. Notch filter 519 filters out signals at frequencies that, if actedupon by focus servo algorithm 501, would excite mechanical resonances indrive 100, for example in actuator arm 104. In general, notch filter 519can include any number of filters to remove particular frequencies fromthe FES signal output from phase lead 518. In some embodiments, notchfilter 519 filters out any signal that can excite a mechanical resonanceof actuator arm 104 that occurs at around 6 KHz in some embodiments ofactuator arm 104.

The output signal from notch filter 519 is input to summer 521. Summer521 further receives a signal from focus close 535. Focus close 535,during operation, provides a bias control effort to servo loop 501. Insome embodiments, focus close 535 provides a focus acquire signal thatis summed with the output signal from notch filter 519. In someembodiments, the focus acquire signal operates through focus actuator206 to first move OPU 103 away from optical disk 102 and then to moveOPU 103 back towards optical disk 102 until an FES signal is acquired,after which the focus acquire signal is held constant. When the focusacquire signal is held constant at the bias control effort, servoalgorithm 501 operates with the FES signal measured from the A, C, E, B,D, and F values and is therefore a closed loop (with a variation in theFES signal resulting in a corresponding correction in the focus controlthat is applied to focus actuator 206).

The output signal from summer 521, then, is input to loop gain 522. Loopgain 522 applies a gain designed to set the open-loop bandwidth of servoalgorithm 501 to be a particular amount. For example, in someembodiments the open-loop bandwidth is set at about 1.5 kHz, which meansthat the open loop frequency response of the entire servo loop(including OPU positioner 104, signal processing, and algorithm 501) is0 dB at 1.5 kHz. Although focus loop gain calibration 522 is furtherdiscussed below., in essence a sine wave generated in sine wavegenerator 528 is input to summer 523, resulting in a modulation of focuscontrol which translates into a modulation of the measured FES signal.The resulting response in the signal from summer 521 is monitored bydiscrete Fourier transform (DFT) 527, and DFT 525 in combination withgain calibration 526 in order to set the gain of loop gain amplifier524. In some embodiments where the transfer function at 1.5 kHz shouldbe unity, the sine wave generator provides a 1.5 kHz sine wave functionto summer 523 and gain calibration 526 set the gain of loop gain 524 sothat the overall gain of the 1.5 kHz component of the signal output fromsummer 521 is equal to the overall gain of the 1.5 KHz component of thesignal output from summer 523.

The output signal from loop gain 524 is input to multiplexer 531, alongwith a low-pass filtered version formed in filter 529 and a signal fromsample and hold (S/H) 530. During normal operation, multiplexer 531 isset to output the output signal from loop gain 524. Although much of theoptical cross-talk is canceled from the control effort signal at summer513, there is still enough cross talk so that, while OPU 103 is crossingtracks on optical media 102, a track crossing component of the controleffort will appear in the output signal of loop gain 524. In someembodiments, seek operations are accomplished at fairly high rates,resulting in a track crossing signal of the order of a few kHz.Therefore, during a seek operation a low-pass filtered version of theoutput signal from loop gain 524 can be substituted for the signal fromloop gain 524. In some embodiments, the output signal from a sample andhold (S/H) 530 circuit can be substituted for the signal from loop gain524 by multiplexer 531. The effects of changing FES as OPU 103 passesover multiple tracks can then be prevented from translating into acorresponding movement of OPU 103.

In a one-track jump operation, there is a similar concern about effectson the FES signal from crossing tracks (i.e., TES-FES crosstalk). Insome embodiments, in a one-track jump, the output signal from sample andhold (S/H) 530 is output from multiplexer 531. Sample and hold (S/H) 530holds the output signal to match that of previous output signals so thatthe resulting control effort is simply held constant through theone-track jump operation.

The output signal from multiplexer 531 is input to summer 533. Theoutput signal from summer 533 is, then, the control effort signal thatis input to focus DAC 464 (FIG. 4) from DSP 416 and then to power driver340 to result in a current being applied to focus actuator 206 toprovide focus. In summer 533, the output signal from multiplexer 531 issummed with an output signal from feed-forward loop 532. Feed-forwardloop 532 inputs the output signal from multiplexer 531 and attempts topredict any regularly occurring motion of OPU 103 relative to opticalmedia 102. These motions occur, for example, because optical media 102is not flat and the surface of optical media 102 will vary in a regularway as optical media 102 is spun. As a result, left alone, there will bea FES generated having the same harmonic as the rotational rate ofoptical media 102. Feed-forward loop 532 provides these harmonics tosummer 533 so that the control effort includes these regular harmonics.In that case, the FES signal calculated from signals A, C, E, B, F, Dwill not include these regular harmonics. In some embodiments,feed-forward loop 532 responds to multiple harmonics of any such regularmotion of OPU 103 so that none of the harmonics are included in thecalculated FES signal.

In order to determine if the focus is OK, a sum of all of the detectorsignals A, C, E, B, D and F is calculated in summer 534 and theresultant sum is input to Focus OK block 536. Focus OK block 536compares the overall sum with a focus threshold value generated by FESGain calibration 510 and, if the sum is greater than the focusthreshold, indicates a focus OK condition. If, however, the sum is lessthan the focus threshold, then a focus open signal is generated by focusOK block 536. In some embodiments, focus OK block 536 may indicate anopen focus condition only after the sum signal has dropped below thefocus threshold for a certain period of time. This will prevent a defectsituation (e.g., a dust particle) from causing servo algorithm 501 tolose (i.e., open) focus.

The output signal from summer 534 is also input to defect detector 591.Defect detector 591 monitors a high-pass filtered sum signal to identifythe presence of media defects. In some embodiments, if the high-passfiltered sum signal exceeds a threshold value then the presence of adefect is indicated. In some embodiments, defect detector 591 candetermine whether or not changes in the sum signal from summer 534 arethe result of changes in laser power (for example in transitions fromread to write or write to read or in spiraling over previously writtendata) as media defects. In some embodiments, defect detector 591 will“time-out” if the defect appears to remain present for a long period oftime, which under that condition may indicate other than a media defect.

In some embodiments, defect detector 591 detects defects by detectingsudden changes in the sum signal. A change in laser power can result ina sudden changes in the sum signal which can be falsely identified as adefect. In some embodiments, a laser servo controller can inform defectdetector 591 of changes in laser power. Once defect detector 591 isnotified of a change, then defect detector can delay for a time period(for example about 5 ms) to allow the sum signal and transients from asum signal low pass filter in defect detector 591 to settle beforeproceeding to detect detects. Notification of defect detector 591 beforea laser power change can reduce the risk of falsely identifying adefect. In some embodiments, defect detector 591, which can be executedon DSP 416, can monitor the focus sum threshold value, which can bechanged in by microprocessor 432 when laser power is changed. Defectdetector 591 can then by notified of changes in laser power by thechange in focus sum threshold value.

Additionally, the sum signal can change when crossing media types (e.g.,from premastered to writeable or from writeable to premastered). In someembodiments, multi-track seek algorithm 557 knows when a boundarycrossing will occur. In some embodiments, multi-track seek algorithm 557can inform defect detector 591 when a boundary is crossed so that afalse defect detection at a boundary crossing does not occur. In someembodiments, the defect threshold value, the threshold value againstwhich the sum signal is compared to detect defects, can be set largeenough to not respond to changes in reflectivity associated with a mediatype boundary change. However, if the defect threshold value is set toohigh defects may not be detected.

Sliding Notch Filter 595 can reduce the effects of optical cross-talk(TES into FES) during multi-track seek operations. Multi-track seekcontroller 557 can be a velocity controlled servo controller. Slidingnotch filter 595 can track the seek reference velocity of multi-trackseek controller 557. For example, the maximum reference velocity couldbe 10 kHz and the minimum reference velocity could be 2 kHz. Slidingnotch filter 595 can vary it's center frequency from 10 kHz to 2 kHz asa function of the seek reference velocity multi-track seek controller557.

Tracking servo algorithm 502, in many respects, is similar in operationto focus servo algorithm 501. In some embodiments, tracking servoalgorithm 502, when closed, inputs detector signals A, C, B, and D andcalculates a tracking error signal TES from which a tracking controleffort is determined. In some embodiments a coarse tracking controleffort, which is output from loop gain calibration 562, and a coarsetracking control effort, which is output from feedforward control 585,can be output.

Detector signals A and C are input to block 538, which calculates atracking error signals TES₁ according toTES ₁=(A−C)/(A+C),such as is described with FIG. 2P. Detector signals B and D are input toblock 539, which calculates TES₂ according toTES ₂=(B−D)/(B+D),such as described with FIG. 2Q. The difference between TES₁ and TES₂ iscalculated in summer 540 to form a TES input signal, as is describedwith FIG. 2R. The TES input signal responds to variation in the trackingmotion of OPU 103 (as controlled by tracking actuator 201) as discussedabove with the analog versions of signals A, C, E, B, D, and F, forexample, with FIGS. 2M through 2R. In some embodiments, furtherprocessing of the TES signal may be performed, for example to reducecross-talk.

The TES signal output from summer 540 is input to summer 541, where itis summed with an offset value. The offset value is determined by TESoffset calibration 542. The output signal from offset summer 541 isinput to TES gain 543, which calibrates the peak-to-peak value of theTES signal in accordance with a TES gain calibration algorithm 544. Asdiscussed above, the TES signal as a function of tracking position is asine wave. As discussed below, in some embodiments the TES offset valuecan be determined to be the center point between the maximum and minimumpeaks of the TES sine wave. Additionally, in some embodiments the TESoffset value can be affected by a determination of the optimum value ofthe TES offset value for data reads or writes and may vary for differingtracking positions across optical media 102. In some embodiments, theTES gain calibration is set so that the peak-to-peak value of theresulting TES signal output from TES gain is at a preset peak-to-peakvalue. The preset peak-to-peak value is selected to provide the bestdynamic range over the range of tracking motion of OPU 103.

Information regarding the peak-to-peak value of the TES signal as afunction of position on optical media 102 can be determined in TES P-P545. In an open tracking situation, the TES signal varies through itsrange of motions as tracks are crossed by OPU 103. TES P-P 545, in someembodiments, records the highest and lowest values of the TES signal asthe peak-to-peak values. In some embodiments, an average of the highestand lowest values of the TES signal is recorded as the peak-to-peakvalues. The peak-to-peak values can be input to Offset calibration 542which calculates the center point and gain calibration 544, whichcalculates the gain required to adjust the peak-to-peak values to thepreset value.

The TES signal output from offset 541 is input to TES gain 543. TES gain543 can, in some embodiments, be calibrated by TES offset calibration542. Calibration algorithms, such as TES offset calibration 542, arefurther described below.

The TES signal output from TES gain 543 is input to TES inversenon-linearity 546. TES inverse non-linearity 546 operates to linearizethe TES signal around the operating point determined by the TES offset,as was discussed above with respect to FES inverse non-linearity 511.Calibration 547 can calculate the gain of TES non-linearity 546 forvarious values of TES offset to linearize the TES signal as a functionof position about the operating point.

The output signal from TES inverse non-linearity 546 is input to TESsample integrity test 548. TES sample integrity test 548 operates withthe TES signal in much the same fashion as FES sample integrity test 515operates with the FES signal, which is discussed above. In someembodiments, TES sample integrity test 548 can be enabled with anenablement signal. When TES sample integrity test 548 is not enabled,then the output signal from TES sample integrity test 548 is the same asthe input signal to TES sample integrity test 548.

The input signal to TES sample integrity test 548 and the input signalto FES sample integrity test 515 and a defect signal produced by defectdetector 591 are input to write abort algorithm 537, which determineswhether, in a write operation, the write should be aborted. If itappears from FES or TES that TES or FES is too large (i.e., one of TESand FES has exceeded a threshold limit), then write abort 537 aborts awrite operation to the optical media 102 by providing an abort writeflag. However, if TES or FES exceeds the threshold limits and defectdetector 591 indicates a defect, the write is not aborted. In someembodiments, low pass filtered FES and TES values are utilized todetermine whether FES or TES are too large. Low pass filtered FES andTES values can essentially include the DC components of the FES and TESsignals. A programmable number N, for example 2, consecutive sampleswith TES or FES above limits and a defect indicated are allowed beforewrite abort 537 aborts a write operation. Aborting the write can preventdamage to optical media 102 due to the high power of laser 218, whichcrystallizes the amorphous material on the writeable portion of opticalmedia 102. Further, damage to adjacent track data can also be prevented.

The output signal from TES sample integrity test, TES′, is, in a closedtracking situation, input to low frequency integrator 549 and then tophase lead 550. Low frequency integrator 549 and phase lead 550 operatesimilarly to low frequency integrator 516 and phase lead 518 of focusservo algorithm 501. Again, in order to provide better response to lowfrequency portions of TES, low frequency integrator 516 and phase lead518 can be second order filters. As discussed previously, a second orderlow frequency integrator provides more low frequency gain, providingbetter error rejection, than a first order integrator. Additionally, asecond order phase lead compensator provides increased phase advance orphase margin at the servo open loop bandwidth than that of a first orderphase lead compensator. The second order phase lead compensator alsocauses less high frequency amplification than that of a first orderphase lead for the same amount of phase advance at the crossover.

The output signal from phase lead 550 is input to notch filter 551.Notch filter 551 can be calibrated by notch calibration 552. Again,notch filter 551 prevents control efforts having frequencies that excitemechanical resonances in actuator arm 104. These mechanical resonancescan be well known in nature (depending on the structure of actuator arm104) but may vary slightly between different drives. The output signalfrom notch filter 551 can be input to a second notch filter 553 in orderthat fixed and known resonances can be filtered. Notch filter 551 andnotch filter 553 can each include multiple notch filters.

In some embodiments, the output signal from notch filter 553 is input toa retro-rocket loop gain amplifier 830. Retro rocket 830 providesadditional gain to tracking servo loop 501 after execution of amulti-track seek operation in order to more aggressively close trackingon a target track. Retro rocket 830 is enabled by multi-track seekcontroller 557.

In a closed-tracking mode, switch 556 is closed and the output signalfrom notch filter 553 is input to multiplexer 558. Again, in a closedtracking mode, multiplexer 558 provides the output signal from notchfilter 553 to loop gain calibration 562. As discussed above with respectto focus loop gain calibration 522, loop gain calibration 562 arrangesthat the frequency response at a selected frequency is 0 dB. To do that,a sine wave generated in generator 568 is added to the control effort insummer 563 and the response in input signal to gain calibration 562 ismonitored. The input signal is provided through Discrete FourierTransform (DFT) 567 to gain calibration 566, along with the outputsignal from summer 563 processed through DFT 565. Gain calculation 566,then, sets the gain of loop gain 564 so that the open loop gain has 0 dBof attenuation at that frequency. The bandwidth set by loop gaincalibration 562 may differ from the bandwidth set by focus loop gaincalibration 522.

Switch 556 is closed by close tracking algorithm 555. When tracking isopen, the TES signal is a sine wave as tracks pass below OPU 103. Theperiod of the sine wave represents the time between track crossings.Tracking can be closed near, for example, the positive slopingzero-crossing of the TES versus position curve (see FIG. 2R). If a trackclosing is attempted at a zero-crossing with the improper slope,tracking servo algorithm 502 will operate to push OPU 103 into aposition at the zero-crossing with the proper slope.

In some embodiments, TZC detector 554 receives the TES′ signal from TESsample integrity test 548 and determines the track zero-crossings TZCand the TZC period, which indicates how fast tracks are crossing underOPU 103. In some embodiments, TZC can be input from tracking crossingdetector 454 and that TZC value can be utilized to compute the TZCperiod. If the track crossings are at too high a frequency, thentracking algorithm 502 may be unable to acquire tracking on a track.However, in another part of the rotation of optical media 102 the trackcrossing frequency will become lower, providing an opportunity toacquire tracking. In some embodiments, close tracking algorithm 555 canreduce the angular speed of spin motor 101 if the track crossingfrequency is too high.

Therefore, when close tracking algorithm 555 is commanded to closetracking, close tracking algorithm 555 monitors the TZC period and, whenthe TZC period gets high enough (i.e., the frequency of track crossingsgets low enough), tracking algorithm 555 closes switch 556 to closetracking servo loop algorithm 502 to operate closed loop on a track.However, there can be large transients when switch 556 is closed becauseOPU 103 can have some initial velocity with respect to the track whenswitch 556 is closed. Therefore, the lower the frequency of crossing(indicating a lower speed of OPU 103 with respect to the tracks), thelower the transients caused by closing switch 556. Prior and duringclosing of switch 556, the low frequency integrator 549 is disabled by aenable signal from close tracking algorithm 555.

In some embodiments, the output signal from loop gain 564 provides afine control effort. In some embodiments, tracking DAC 468 (FIG. 4) isan 8-bit digital-to-analog converter. Tracking actuator 201, however,needs to move OPU 103 from the inner diameter (ID) of optical media 102to the outer diameter (OD) of optical media 102. Therefore, althoughactuator arm 104 must move OPU 103 from ID to OD, while tracking isclosed small motions of OPU 103 around the tracking position arerequired. For example, in some embodiments when tracking is closed OPU103 moves in the range of approximately ±70 nm around a centralposition. Further, in some embodiments a full stroke from ID to OD isapproximately ¼ inch to a ½ inch. In addition to the large dynamic rangerequired to move OPU 103 from ID to OD on optical media 102, there isalso a spring force in the mounting of spindle 203 of actuator arm 104to overcome.

Therefore, in some embodiments of the invention a second DAC convertercan be utilized as a coarse actuator control while the control effortfrom loop gain 564 can be utilized as a fine actuator control. Thetracking control effort signal output from loop gain 564, then, is inputto tracking DAC 468 (FIG. 4). Tracking DAC 468 can have any number ofbits of accuracy, but in some embodiments includes an 8-bit digital toanalog converter.

In some embodiments, a coarse tracking control effort is generated bybias feedforward control 585. The coarse tracking control effortgenerated by bias feedforward control 585 can be the low-frequencycomponent of the tracking control effort produced by loop gain 564. Thecoarse tracking control effort, then, can be communicated tomicroprocessor 432, which can then transfer the coarse control effort topower driver 340 (FIG. 3A) through serial interface 458. A seconddigital-to-analog converter in power driver 340, in some embodimentshaving an accuracy of 14 bits, receives the coarse control effort frommicroprocessor 432 through serial interface 458. In power drive 340, theanalog course control effort is then summed with the analog fine controleffort from DAC 468 to provide the whole tracking control current totracking actuator 201. Therefore, microprocessor 432 can determine thelow frequency component of the tracking control effort in order to biastracking actuator 201 while DSP 416, executing tracking servo algorithm502, determines the fine tracking control effort to hold OPU 103 ontrack.

In some embodiments, the output signal from loop gain 564 is input toanti-skate algorithm 593. Anti-skate algorithm 593 receives a directionsignal from direction detector 592 and an anti-skate enable signal fromtracking skate detector 561. Anti-skate algorithm 593, when enabled,determines which TES slope is stable and which is unstable. The stableslope will be different for the two opposite directions of motion of OPU103 relative to optical media 102. For example, if a positive slopingTES signal is stable when OPU 103 is traveling from the inner diameter(ID) to the outer diameter (OD), the negative sloping TES signal isstable when OPU 103 is traveling from the OD to the ID. Anti-skatealgorithm 593, then, prevents tracking control loop 502 from closing onan unstable slope, which can prevent further skating from attempting toclose on the unstable slope. During periods when the tracking errorsignal indicates an unstable slope, a substitute tracking control effortcan be substituted for the tracking control effort received fromtracking servo system 502. Anti-skate algorithm 593 allows trackingcontrol algorithm 502 to more easily close onto a track once asignificant disturbance has caused the tracking servo to slide acrossseveral tracks (i.e. skate).

Bias control 585 receives the control effort signal from loop gain 564through anti-skate algorithm 502. Low pass filter 569, which can be a200 Hz second order filter, receives the tracking control effort andpasses only the low frequency component. The sign of the signal outputfrom low pass filter 569 is detected in sign 570. The sign adds a setamount (for example +1, 0, or −1) to a track and hold circuit thatincludes summer 574 and feedback delay 575. With 0 inputs to summer 574,the output signal from summer 574 will be the last output signalreceived, as is stored in delay 575. Sign 570, then, determines whetherto increase the bias value of the coarse control effort or decrease thebias value of the coarse control effort. Since the decision to increaseor decrease the coarse control effort occurs only during an interruptcycle of microprocessor 432, and since a single increment or decrementis made per cycle, the course control effort resulting from bias forwardcontrol 585 varies very slowly (for example, one increment every 2 ms).

In operations, bias control 585 essentially removes the low frequencycomponent of the fine tracking control effort output from loop gain 564by transferring the low frequency control effort to coarse controleffort output from bias control 585. A constant control effort appearingon the fine tracking control effort, for example, will eventually betotally transferred to the coarse tracking control effort output frombias control 585. However, if the interaction between the fine trackingcontrol effort and the coarse tracking control effort is too fast, therecan be stability problems. Therefore, there is incentive to make biascontrol 585 respond slowly to changes in the low frequency component ofthe tracking control effort output from loop gain 564. The incrementingor decrementing of the coarse control effort output from bias control585 occurs during the regular interrupt time (Ts) for operatingmicroprocessor 432, which can in some embodiments be about 2milliseconds.

In a closed tracking mode, the coarse control effort signal output fromsummer 578 changes very slowly. However, during seek operations there isa need to change the coarse control effort signal much more quickly.Therefore, during seek operations, the output signal from low passfilter 569 is further filtered through low pass filter 571. A portion(indicated by K multiplier in block 576) is added in summer 574 to thecoarse control effort and to summer 578, whose output is the coarsecontrol effort. Therefore, during seek operations the coarse controleffort output from bias control 585 can change quickly. Low pass filter571 allows frequencies low enough (e.g., less than about 20 Hz) to allowthe seek control effort to increase the coarse control effort fasterthan the incremental changes allowed by switch 573 but is of low enoughfrequency that other disturbances do not affect the coarse controleffort output by summer 578.

Additionally, the output signal from low pass filter 569 is input tooff-disk detection algorithm 572, which monitors very low frequencycomponents. Since very low frequency components of the TES are amplifieda great deal through integrator 549 and phase lead 550, an essentiallyDC component of TES will have a large gain and, therefore, will be alarge component of the tracking control effort output from loop gain564. This low frequency component is not filtered by low-pass filter 569and, therefore, is input to off-disk detection algorithm 572. If a largeDC signal is observed over a period of time, off-disk detectionalgorithm 572 concludes that OPU 103 is outside of the operational rangeof optical media 102 and provides an error message to microprocessor432. Microprocessor 432, as described in the System Architecturedisclosures, then takes the appropriate error recovery steps.

In some embodiments, a calibrated tracking feed-forward control 579 canalso be included. Feed-forward control 579 can determine any regularvariations in the tracking control effort produced by loop gain 564 andinsert a corresponding harmonic effort into the tracking control effortin order to anticipate the required motion of OPU 103. Those harmonics,then, would be subtracted from the TES.

When close tracking algorithm 555 closes tracking, in some embodimentsintegrator 549 and sample integrity test 548 may be disabled when switch556 is first closed. This will increase the damping, at the cost ofreduced low frequency gain, in tracking servo loop algorithm 502. Onceswitch 556 is closed, close tracking algorithm 555 may wait some timefor any transient effects to decay before enabling integrator 549 andthen enabling sample integrity test 548. In other words, before the lowfrequency components of TES are boosted by integrator 549, servo loopalgorithm 502 and actuator arm 104 have settled close to the desiredtracking position.

The TES′ signal from sample integrity test 548 can also be input tomulti-track seek controller 557, one track jump control 559, andtracking skate detector 561. Multi-track seek controller 557, in amulti-track seek operation, supplies a control effort to multiplexer 558which, when selected, causes actuator arm 104 to move OPU 103 near to atarget track on optical media 102. After OPU 103 is at or near thetarget track, then close tracking algorithm 555 can be activated toclose tracking at or near the target track. One track jump algorithm559, which can be calibrated by a calibration algorithm 560, outputs acontrol effort signal to multiplexer 558 which, when selected, moves OPU103 by one track. In some embodiments, a large motion of OPU 103 can beundertaken by multi-track seek controller 557 and then one track jumpcontrol 559 can operate to move OPU 103 closer to the target trackbefore tracking is closed by close tracking algorithm 555. Trackingskate detector 561 monitors FES′ and indicates when tracking has beenopened. If tracking skate detector 561 indicates an open trackingcondition, then tracking may need to be reacquired. Furthermore,tracking skate detector 561 enables anti-skate algorithm 593. A signalcan be sent to microprocessor 432 so that microprocessor 432 can executeerror recovery algorithms, which in this case may involve reacquiringtracking long enough to determine the position of OPU 103 and thenperforming a seek operation to move OPU 103 to the selected track andreacquiring tracking at the selected track. See the System ArchitectureDisclosures.

FIGS. 5E and 5F show an embodiment of tracking skate detector 561. Asshown in FIGS. 5E and 5B, tracking skate detector 561 receives the TES′signal from TES sample integrity test 548. As shown in FIG. 5F, as OPU103 moves across tracks the TES′ signal shows a sinusoidal signal. Theabsolute value of the TES′ signal is calculated in block 594. The outputsignal from absolute value block 594 is then input to low pass filter595. In effect, low pass filter 595 can act as an integrator. The outputsignal from low pass filter 595 is input to compare block 598 where itis compared with an anti-skate threshold. The output signal from compareblock 598 is input to threshold counter 599. If the output signal fromlow pass filter 595 exceeds the anti-skate threshold more than a maximumnumber of clock cycles, then counter 599 sets the enable anti-skateflag, enabling anti-skate algorithm 593.

The output signal from low pass filter 595 is also input to compareblock 596. Compare block 596 compares the output signal from low passfilter 595 with a skate threshold, which is typically larger than theanti-skate threshold. The output signal from compare block 596 is inputto counter 597. If the skate threshold is exceeded for a maximum numberof cycles, then counter 597 outputs a skate detected flag. The skatedetected flag can then indicate that tracking is open.

FIG. 5G shows an embodiment of direction sensor 592. Direction sensor592 determines the direction that optical pick-up unit 103 is travelingradially across the surface of optical pick-up unit 103. Summer 5001sums the optical signals from outside elements of detectors 225 and 226(FIG. 2D), elements 231, 233, 234 and 236, to form a direction sumsignal. In some elements, more or less than two detectors are includingin optical pick-up unit 103. The direction sum signal from summer 5001includes both DC and AC components. The DC component of the directionsum signal represents the laser intensity of laser 218. The AC componentof the direction sum signal is dominated by a quadrature signal, whichlooks similar to TES when crossing tracks except that it is 90 degreesout of phase with the TES. In some embodiments, for example, thedirection sum signal can be 90 degrees phase advanced when travelingfrom the inner diameter (ID) to the outer diameter (OD) of optical media102 (FIG. 1B) and 90 degrees phase lagged when traveling from OD to IDof optical media 102.

The direction sum signal is input to sample and hold 5002 while the TES,for example from the output signal from summer 541, is input to sampleand hold 5003. Media defects on optical media 102 can cause erroneousdirection sum signals and TES signals, therefore the Sample and Hold S/Hfunctions 5002 and 5003 hold the high pass filter input signals constantduring the presence of a media defect, indicated by the defect signalfrom defect detector 591.

The output signals from sample and holds 5002 and 5003 are input to highpass filters 5004 and 5005, respectively. The disk reflectivity ofoptical media 102 varies as a function of disk angular orientationresulting in an undesirable AC signal at the first harmonic of therotation frequency of optical media 102. The High Pass filter cutofffrequency of filters 5004 and 5005, then, can attenuate the firstharmonic reflectivity variation signal. The output signal from High Passfilter 5004, SumHp, is an AC signal representing the quadraturecomponent from the sum signal. Block 5006 converts the analog SumHpsignal into a digital logic signal SumHpD, depending on whether SumHp isgreater than or less than zero. High Pass Filter 5004 introduced a phaseshift into the resulting SumHpD. High Pass Filter 5005 introduces thesame phase shift into the TES in order to form a TESHpD signal, whichthen has a matching phase shift. Similarly, block 5007 converts theTESHpD signal into a logic signal by comparing the TESHpD signal withzero. Logic blocks 5007, 5008, 5009, 5010 and 5011 together perform thefollowing logic function:Direction′=(TESHpD AND SumHpD) OR ( TESHpD AND SumHpD)The polarity of the direction sensor changes between Mastered andWrite-able media. Inverter 5012 inverts Direction′ and switch 5013outputs a direction signal from the output signal of inverter 5012 orfrom direction′, depending on whether OPU 103 is over mastered orwrite-able media.

FIG. 6 shows an embodiment of a close tracking algorithm 555 (FIG. 5B).Close tracking algorithm 555 closes tracking servo algorithm 502 andtherefore acquires tracking. In step 601, algorithm 555 receives acommand to close tracking. The close tracking command can originate frommicroprocessor 432 or from another algorithm executing in DSP 416. Oncethe close tracking command is received, algorithm 555 proceeds to step611

In step 611, the TES gain is set based on the peak-to-peak value of theTES signal. In some embodiments, the TES gain can be set for groovecrossings or bumps. From step 611, algorithm 555 proceeds to step 602.

In step 602, algorithm 555 determines the TZC period in order todetermine the track crossing speed, indicating the relative velocitybetween OPU 103 and the tracks on optical media 102. The track crossingspeed is related to the period of track crossing parameter TZC, whichcan be determined from TZC detector 554 or can be calculated from TES′.

After the track crossing speed is determined in step 602, algorithm 555checks for a time-out condition in step 603 by determining whether toomuch time has passed since the close tracking command was received instep 601. If too much time has passed, a microprocessor time-out flag isset and microprocessor 432 proceeds to an error recovery routine.Otherwise, algorithm 555 proceeds to step 604.

Step 604 determines if the track crossing rate is too high to closetracking. Step 604 can determine if the track crossing rate is too high,for example, by comparing the TZC period with a track close threshold.If the threshold is not exceeded, then the track crossing rate is toohigh and algorithm 555 returns to step 602. If the track crossing rateis low enough, then algorithm 555 continues to step 605.

In step 605, close tracking algorithm 555 closes switch 556, therebyclosing the tracking servo loop. When switch 556 is first closed,integrator 549 and integrity test 548 are disabled to allow betterresponse of the tracking servo loop while transient effects decay. Onceswitch 556 is closed, algorithm 555 proceeds to step 606.

In step 606, algorithm 555 delays long enough for transient effects fromclosing switch 556 to decay. Once a particular delay time period haselapsed, algorithm 555 proceeds to step 607 where integrator 549 isenabled. Enabling integrator 549 introduces a new set of transienteffects. Therefore, once integrator 549 is enabled, algorithm 555proceeds to step 608, which waits for another delay time. Once thesecond delay time has elapsed, algorithm 555 proceeds to step 609 whereTES sample integrity test 548 is enabled.

Once step 609 is complete, algorithm 555 proceeds to stop 610 where atracking closed flag can be sent to either microprocessor 432 or DSP416, depending on where the original close tracking command originated.In some embodiments of the invention, algorithm 555 is performed as ajoin effort between both microprocessor 432 and DSP 416. For example,microprocessor 432 may command DSP 416 to close loop in step 601. DSP416 receives TZC period in step 602 and checks to see if the TZC isbelow a TZC threshold in step 604. Meanwhile, microprocessor 432 beginsa time-out clock. If DSP 416 has not closed switch 556 within thetime-out period, then microprocessor 432 proceeds to error recovery.Once switch 556 is closed, DSP 416 will not proceed on this algorithmuntil, in step 607, microprocessor 432 tells DSP 416 to enableintegrator 549. Microprocessor 432 controls the relative timing, whilethe DSP 416 is slaved and only responds to commands from microprocessor432. Further, once integrator 549 is enabled in step 607, microprocessor432 then can tell DSP 419 to enable sample integrity test 548. In someembodiments, without commands from microprocessor 432, DSP 419 will notchange state.

FIG. 7A shows a block diagram of an embodiment of focus close algorithm535. Focus close algorithm 535 asserts control efforts onto the focuscontrol effort through summer 521. In some embodiments, summer 521 maybe replaced with a switch or multiplexer circuit that chooses a controleffort originating from focus close algorithm 535 or from notch filter519.

Algorithm 535, in some embodiments, starts with a control effort so thatOPU 103 is positioned away from optical media 102 (i.e., the distancebetween OPU 103 and optical media 102 is larger than the focusdistance). Algorithm 535 then generates a control effort to move OPU 103closer to optical media 102 until the control effort is appropriate fora focus distance. Once OPU 103 is near the focus distance, thenalgorithm 535 holds its contribution to the control effort constantwhile the focus servo loop 501 generates the additional focus controleffort required to maintain closed loop focus.

In step 701, a focus acquire flag is set. The focus acquire flag can beset by a routine executing in microprocessor 432 or in DSP 416. In step703, algorithm 535 determines whether the actuator is positionedappropriately to start a focus acquisition procedure. This can be testedby setting a range of values for the current focus control effort or bycomparing with a threshold value for the focus control effort. In someembodiments, the current in focus actuator 206 is zero and algorithm 535needs to push OPU 103 away from optical media 102.

If the control effort for focus actuator 206 is not positionedappropriately, then algorithm 535 must generate a focus control effortappropriate to move OPU 103 to an acceptable starting point. Inaddition, algorithm 535 should provide a control effort that moves OPU103 in such a way as to not excite mechanical resonances in actuator arm104. For example, if a focus control effort profile is generated byalgorithm 535 that simply sets the focus control effort to a valuecalculated to be the value at the acquisition starting position, manymechanical resonances are likely to be excited in actuator arm 104.Should mechanical resonances in actuator arm 104 become excited, theremay be transient motions generated with large decay times, increasingsignificantly the amount of time required for focus acquisition. In someembodiments, in step 704 algorithm 535 generates a sinusoidal startingfocus control effort profile which moves OPU 103 to an acquisitionstarting position in a smooth fashion.

FIG. 7B shows an example of a starting focus control effort profilegenerated in step 704. Step 704 generates a sine wave with one peakbeing at the current focus control effort (indicating the currentposition of OPU 103 relative to optical media 102) and the opposite peakbeing at the acquisition starting position control effort. The startingfocus control effort can be applied to focus actuator 206 in step 705 byadding the starting focus control effort into the focus control effortat summer 521. This method of positioning elements, in both the focusand the tracking directions, can be widely utilized. In other words,whenever OPU 103 needs to be positioned relative to optical media 102, asmooth control effort as described above can be generated and applied.The resulting smooth motion of OPU 103 can reduce excitations ofmechanical resonances which may be obtained by application of moreabrupt control efforts.

If, in step 703, OPU 103 is already at an appropriate startingacquisition position, then algorithm 535 proceeds to step 706.Additionally, after the starting control effort is applied to focusactuator 206, then algorithm 535 proceeds to step 706.

In step 706, algorithm 535 generates an acquisition control effort thatmoves OPU 103 from the starting acquisition position through the bestfocus position. Algorithm 535, in some embodiments, can provide thefocus acquisition control effort required to move OPU 103 from thestarting acquisition position through the best focus position. However,again if mechanical resonances are excited in actuator arm 104, it maytake some time for the transient oscillations to damp out. Therefore, insome embodiments, step 706 calculates a sinusoidal focus acquisitioncontrol effort between the starting acquisition position and the controleffort corresponding to a position close to optical media 102. In someembodiments, the position close to optical media 102 may be the closestposition that OPU 103 can be moved toward optical media 102. Such afocus acquisition control effort profile is shown in FIG. 7C.

Once the focus acquisition control effort profile is calculated, then instep 707 DSP 416 is enabled to monitor the sum signal from summer 534,which generates the sum of all of the detector signals A, B, C, D, E,and F, and the FES signal output signal from summer 513 in order todetermine when focus has been acquired. In step 708, the focusacquisition control effort according to the focus acquisition controleffort profile calculated in step 706 is applied through summer 521 tothe focus control effort, and therefore applied to focus actuator 206 inorder to physically move OPU 103 through the best focus position.

In step 710, algorithm 535 monitors the closure criteria during theapplication of the focus acquisition control effort profile. If theclosure criteria is not satisfied, then algorithm 535 proceeds to step711. In step 711, algorithm 535 checks to see if the closest positionhas been reached. If in step 711, it is determined that OPU 103 has notyet reached the closest position, then algorithm 535 proceeds to step708 to continue to apply the focus acquisition control effort profile asthe focus control effort.

Step 710 can determine whether OPU 103 is close to the focus position,in some embodiments, by the sum signal output from summer 534. In thatcase, if the sum signal is above a focus sum threshold determined by FESgain calibration 510, then OPU 103 is near to the focus position.Furthermore, close to the focus position the FES signal will be nearzero. Therefore, in some embodiments the closure criteria of step 710can be that the sum signal is above a sum threshold and the FES signalis below an FES threshold.

If in step 710 algorithm 535 determines that the closure criteria issatisfied, algorithm 535 proceeds to step 712. In step 712, algorithm535 closes the focus loop without integrator 516 being enabled.Algorithm 535 then sets the current focus control effort to the biascontrol effort. In that case, step 712 maintains the focus controleffort from the acquisition focus control effort profile when the closedcriteria was satisfied. The acquisition focus control effort is heldconstant by algorithm 535 when focus is closed as long as focus remainsclosed.

In step 714, algorithm 535 delays for transient effects to decay beforeturning integrator 516 on in step 716. Algorithm 535 can further delayin step 718 for transient effects to decay before enabling FES sampleintegrity test 515 in step 720. Once focus is closed and integrator 516and sample integrity test 515 are enabled, a focus acquisition completeflag can be set in step 723. In some embodiments, the “begin acquisitionposition” of step 704 may be recalibrated and stored for futureexecutions of algorithm 535 in step 723.

If the closure condition of step 710 is not met, algorithm 535 proceedsto closest position check step 711. If algorithm 535 determines in step711 that OPU 103 is at a closest position to optical media 102, thenalgorithm 535 sets a focus error bit in step 713. In some embodiments,the closest position can be the physically closest distance that OPU 103can be from optical media 102. In some other embodiments, however, theclosest position refers to a closest allowable position that can be apredetermined value.

Once the focus error bit is set in step 713, algorithm 535 can proceedto step 715. In step 715, algorithm 535 determines a sinusoidal trackingcontrol effort profile that moves OPU 103 away from optical media 102 toa focus off position. As before, the sinusoidal tracking control effortcan be determined, as is shown in FIG. 7D, by fitting a half sine wavebetween the closest position and the focus off position. A focus controleffort according to the sinusoidal tracking control effort is applied tofocus actuator 206 in step 717. Once OPU 103 has reached the focus offposition in step 719, then algorithm 535 exits in a failed condition instep 721. If focus acquisition fails, then error recovery routines canbe initiated as is described in the System Architecture disclosures. Insome embodiments, the error recovery routines can attempt to executefocus close algorithm 535 multiple times or change the “BeginAcquisition Position” in step 704 of algorithm 535 shown in FIG. 7A.

FIGS. 8A and 8B illustrate an embodiment of multi-track seek algorithm557. FIG. 8A shows a block diagram of an embodiment of multi-track seekalgorithm 557 while FIG. 8B shows signals as a function of time forperforming a multi-track seek function according to the presentinvention.

FIG. 8B shows the TES, tracking control effort, FES, and focus controleffort signals during a multi-track seek operation performed byalgorithm 557. During time period 821, focus servo algorithm 501 andtracking servo algorithm 502 are both on and tracking. At the beginningseek period 822, algorithm 557 generates a seek tracking control effortprofile which includes an acceleration tracking control effort 825 and adeceleration tracking control effort 827. A coasting or clamped trackingcontrol effort 826 can also be included between acceleration effort 825and deceleration effort 827.

The TES signal, then, begins to sinusoidally vary when accelerationtracking control effort 825 is applied to tracking actuator 360. Theperiod of the sinusoidal variation indicates the track crossingvelocity. During acceleration, the period is decreasing indicating anincreasing track crossing velocity. In some embodiments, seek algorithm557 may clamp velocity at a particular value. Further, accelerationcontrol effort 825 and deceleration control effort 827 may be calculatedby controlling the actual acceleration of OPU 103 relative to opticalmedia 102 as measured with the varying period of the sinusoidal TES. InFIG. 8B, a track crossing velocity curve that may be generated by seekalgorithm 557 is shown, which indicates a constant acceleration theperiod when acceleration tracking control effort 825 is applied and aconstant deceleration the period when deceleration tracking controleffort 827 is applied. During period 823, seek algorithm 557 reacquiresa tracking on condition in tracking servo algorithm 502.

In some embodiments, during the seek operation the FES control effort isselected in multiplexer 531 to be the low-pass filtered focus controleffort output by low pass filter 529 in order that TES-FES crosstalkeffects are minimized. In some embodiments, the output signal fromsample and hold 530 is selected by multiplexer 531 during seekoperations. In some embodiments, seek cross-talk notch filter 590 canalso be enabled during the seek operation in order to reduce the effectsof the sinusoidal TES on FES. Therefore, in operation seek algorithm 557in some embodiments adjusts multiplexer 531 to receive the focus controleffort from filter 529 and can enable notch filter 590. Algorithm 557also adjusts multiplexer 558 to receive a tracking control effortgenerated by algorithm 557, turning tracking servo algorithm 502 off.Algorithm 557 then generates and applies a seek tracking control effortprofile, which is responsive to the velocity of OPU 103, and moves OPU103 to a target track on optical media 102. The velocity of OPU 103 canbe determined by measuring the period of the sinusoidally varying TES.Once algorithm 557 completes the actual move of OPU 103, then trackingis reacquired in close tracking algorithm 555 and multiplexer 558 isreset to receive the focus control effort signal from notch filter 553through switch 556. Further, multiplexer 531 is reset to pass the signaloutput from loop gain 524 as the focus control effort.

FIG. 8A shows a block diagram of an embodiment of algorithm 557. TheTES′ signal output from TES sample integrity test 548 is received byTrack Zero Crossing (TZC) detector 801. TZC detector 801 determines thetrack crossings and, in some embodiments, each time a track is crossedgenerates a pulse signal. In some embodiments of the invention,algorithm 557 may read the TZC signal from track crossing detector 454(see FIG. 4). In some embodiments, TZC detector 801 receives a defectsignal from defect detector 591. The defect signal disables the TZCdetector output from generating a pulse during the presence of a mediadefect. The TZC signal is input to TZC counter 802 and TZC period 803.TZC detector 554 of FIG. 5B includes TZC detector 801 and TZC period803. TZC counter 802 counts the number of tracks crossed. The Directionsignal from Direction Detection 592 determines the direction TZC counter802 counts. For example, if a direction reversal occurs near the end ofa seek possibly due to an external disturbance, then the counter willincrement instead of decrement. This assures the seek crosses thecorrect number of tracks. TZC period 803 calculates the time periodbetween successive track crossings. Seek completion detection 816monitors the number of tracks crossed from TZC counter 802 and indicateswhether seek is complete. Seek complete detection 816, therefore, alsoindicates the number of tracks remaining to the target track. Inaddition, seek complete detection 816 can output a retro-rocket signalwhich can enable retro-rocket gain 830. In some embodiments, seekcompletion 816 indicates that the seek is completed when the countexceeds the target count and when the TES signal has an appropriateslope in which to close tracking.

In some embodiments, TZC counter 802 receives a signal indicating eachfull rotation of optical media 102. During seek operations, opticalmedia 102 continues to rotate. The rotations can cause additive seeklength error to the actual seek length if the seek servo simply countstrack crossings in TZC counter 802 instead of taking the track spiralinto account. Predicting the number of disk rotations based upon seeklength could be used; however, this method does not account for seektime variations caused by outside factors such as, for example,mechanical disturbances. TZC counter 802, by incrementing the TZC countduring seeks on each rotation of optical media 102, can prevent errorsin seek length.

A velocity profile is calculated in reference velocity calculation 805.The velocity profile calculated in reference velocity calculation 805can, as shown in FIG. 8B, be optimized to move OPU 103 to the targettrack in a minimum amount of time without exciting resonances and stopOPU 103 at or very near the target track. FB velocity calculation 806receives the measured track crossing period from TZC period 803 andcalculates the actual velocity of OPU 103. The difference between thereference velocity calculation from calculation 805 and the actualvelocity as calculated by calculation 806 is formed in summer 807, whichoutputs a velocity error value. In some embodiments, the output signalfrom calculation 806 is input to a sign block 818 which, based on thedirection signal from direction detector 592, multiplies the calculatedFbVEL value from block 806 by the sign of the direction signal.

In some embodiments, FB Vel calculation 806 calculates the velocitybased on the time between half-track crossings. In some embodiments, athigher velocities, two consecutive half-track periods can be averaged.The sampling rate of algorithm 557 is the half-track crossing rate,which can be quite low (e.g. 2 kHz at track capture) resulting in a lowbandwidth closed loop seek servo. The low bandwidth leaves the seekservo vulnerable to shock and vibration disturbances during the criticaltrack capture phase of the seek operation. It is desirable to achievegood velocity regulation particularly when approaching the track capturephase of the seek. This bandwidth can be improved, and thus the velocityregulation upon track capture can be improved, by calculating thederivative of the TES when the TES is within a reasonable linear rangeof it's sinusoidal curve while crossing tracks. The derivativemeasurement is averaged with the most recent half track crossingmeasurement to filter some of the inherent noise effects associated withdifferentiation. Additionally, the positive and negative slopes of theTES are not symmetric, therefore, a balance gain is applied to one ofthe TES slopes to eliminate the effect of this asymmetry on thederivative calculation. In these embodiments, then, the FbVEL parameteris given by FbVEL=[(K1/TzcPeriod)+K2*d(TES)/dt]/2, where K2=K2a fortrack enter slopes and K2=K2b for half track center slopes. Typically,K2a=−0.7 K2b.

The velocity error from summer 807 is multiplied by a constant K₃ instep 809 and input to summer 813. Further, velocity error is summed withthe sum of velocity errors measured during previous clock cycles insummer 810, multiplied by constant K₄ in step 812, and added to theoutput value from step 809 in summer 813. Summer 810 acts as anintegrator, integrating the velocity error. The output value from summer813 is input to multiplexer 814. The output signal from multiplexer 814is input to loop gain 815, which generates a tracking control effort.The tracking control effort output by loop gain 815 is part of the seektracking control effort profile which moves OPU 103 to the target trackin a controlled fashion.

In some embodiments, the tracking control effort output from multiplexer814 can be a clamped acceleration effort generated by acceleration clamp808. Acceleration clamp 808 monitors the acceleration of OPU 103 fromthe velocity error determined in summer 807 and, if a maximumacceleration value is exceeded, limits the tracking control effort to bethe maximum acceleration value.

In some embodiments, the TES′ signal is also input to boundary detector817. In general, multi-track seeks can cross boundaries betweenwriteable 151 and pre-mastered 150 portions of optical media 102 (FIG.1B). The operation of direction sensor 592 as well as many operatingparameters, including the TES gain, TES offset, FES gain, FES offset,and cross-talk compensation parameters from cross-talk calibration 579will be different depending on whether OPU 103 is over a writeable orpre-mastered portion of optical media 102. Boundary detector 817includes a multi-point positive and negative TES peak averagingalgorithm, which is executing during seek operations. Boundary detector817 then monitors the TES peak-to-peak amplitude during seeks. Beforeinitiating a seek operation, algorithm 557 knows the type of media (i.e.pre-mastered, grooves, or write able, bumps) that OPU 103 is over.Microprocessor 432 can inform algorithm 557, which is usually operatingon DSP 416, whether or not the seek operation takes OPU 103 from onetype of media to another. If a boundary crossing is detected, thenboundary detector 817 can monitor to determine when the boundary hasbeen crossed.

Boundary detector 817 detects the boundary crossing by identifying whenthe TES peak-to-peak amplitude (TESPP), for example calculated by themulti-point peak averaging, by more than a threshold value (for example25% of TESPP).TesPP Change=|TesPP(k)−TesPP(k−2)|where k represents the measurementnumber.If the threshold value is set too high, the boundary crossing algorithmmay miss boundary crossings. Alternatively, if the threshold value isset too low, the boundary crossing algorithm may erroneously detectboundary crossings. In some embodiments, a default threshold can beutilized for a first boundary crossing on a newly inserted disk. Whenthe boundary is detected, the measured change in TES peak-to-peak valuecan be averaged with the default threshold to drive the thresholdamplitude in the direction of the actual change in TES peak-to-peak forthe specific one of media 102. The averaging process can continue forall subsequent boundary crossings while the specific one of media 102 isin drive 100. The threshold, then, can be set to the averaged thresholdfor all future boundary crossings in that specific media 102.

In some embodiments, consecutive TesPP measurements are not comparedbecause one of these measurements may straddle a boundary between mediawhen making the multipoint peak averaging measurement. At that point,boundary detector 817 determines that the boundary has been crossed andswitches the media sensitive operating parameters to parametersappropriate for the new media.

FIGS. 9A and 9B shows a flow chart of an embodiment of seek algorithm557. In seek initialization 901, seek command 902 is issued, for exampleby microprocessor 432. Further, an acceleration flag, a seek directionflag, a TZC period, and a seeklength (indicating target track) are setin initialization 903. In some embodiments, laser power may be reducedduring a seek operation. Therefore, in seek initialization 901, laserpower can be reduced as well. Upon completion of the seek operation,laser power can be reset to a read power level.

In step 904, a TZC period count variable is incremented. In step 905,the TZC period count variable is checked against the current TZC periodvariable and, if at least half or some other fraction of the mostrecently measured TZC period has not elapsed, algorithm 557 proceeds toskip TZC period and counter calculations 803 and 802. If the conditionof step 905 is met, then algorithm 557 proceeds to crossing detection906. Crossing detection 906 indicates a crossing TZC if the TES′ valuecrosses 0. Crossing detection 906 includes amplitude hysterisis inaddition to the temporal hysterisis provided in step 905, i.e., that thenext TZC crossing can not be indicated again for at least half the oldTZC period value, which prevents noise from falsely indicating a TZCcrossing.

FIG. 9C illustrates the TZC detection algorithm performed by TZCdetector 801. TZC detector 801 provides a change in state on each zerocrossing. As shown, however, TZC detection 906 of TZC detector 801provides a change of state on each detected zero crossing. TZC detection906, from step 905, is enabled to change after about ½ the TZC period.Additionally, in step 906, the TZC crossing provides a low thresholdvalue and a high threshold value so that, on an increasing TES′ signal,the TZC zero is detected at the high threshold value and on a decreasingTES′ signal detects the TZC zero at the low threshold. A amplitudehysterisis is then provided.

In step 907, algorithm 557 indicates whether the TZC value has changed,indicating a track crossing. If not, then calculation of TZC period andupdating of track counting in steps 803 and 802 are skipped. If the TZCvalue has changed, then algorithm 557 proceeds to block 908. In block908, if the acceleration flag is not set or if the current count for TZCperiod (the TZC period count variable) is less than some multiple (forexample twice) of the most recently measured TZC period or if theTZCSkip flag is set, then algorithm 557 proceeds to step 909, elsealgorithm 557 proceeds to step 910 which sets the TZC skip flag. Fromstep 910, algorithm 557 then proceeds to step 913, which resets the TZCperiod count to zero. If the conditions of step 908 are met, thenalgorithm 557 proceeds to step 909.

Step 909 checks whether the currently detected TZC pulse is the firstpulse and, if so, proceeds to step 913 where the TZC period countvariable is set to 0. Otherwise, algorithm 557 proceeds to step 911which sets the TZC period to the current TZC period count. Algorithm 557then clears the TZCskip flag in step 912 before resetting the TZC periodcount in step 913.

Steps 908 through 912, perform a TZC period integrity test. In someembodiments, the TZC period is checked against the previously measuredTZC period (i.e., the TZC period of cycle k is compared with the TZCperiod of cycle k−1). An error is generated if the TZC period of cycle kvaries substantially from the TZC period of cycle k−1. In someembodiments, since a new zero crossing is not detected until at least ½the TZC period of cycle k−1 (see step 905), and step 908 checks to besure that the TZC period in the kth cycle is less than twice the TZCperiod in the k−1th cycle, then the TZC period is restrained to bebetween ½ TZC period and 2 the TZC period of the k−1th cycle (i.e.,TZCperiod(k−1)/2<TZCperiod(k)<2*TZCperiod (k−1). In some embodiments,the range can be extended. For example, in some embodiments TZCperiod(k−1)/4<TZCperiod (k)<4*TZCperiod(k−1).

In step 914, the direction is checked, for example by checking thedirection signal from direction detector 592 (FIG. 5A), so that the TZCcount variable can either be decremented in block 915 or incremented inblock 916, depending on direction. Algorithm 557 then proceeds to step917.

In step 917, algorithm 557 checks if the current calculated referencevelocity, which is a constant times the TZC count parameter calculatedin block 802 of FIG. 8A, is greater than a maximum value of thereference velocity. If the reference velocity is greater than half thevalue of the maximum, then the TZC period value is averaged withprevious TZC period values in step 918, which can have the effect ofsmoothing the actual velocity measurement. Algorithm 557 then proceedsto step 919 of seek completion detection 816.

Step 919 checks the current value of the TZC count to see if therequired number of tracks have been crossed. If not, then algorithm 557proceeds to step 922 of algorithm 805. If the number of track crossingsis correct, then algorithm 557 checks in step 920 to see if the TES′ hasthe correct slope. If not, the algorithm 557 proceeds to step 922. Ifthe slope is correct, then algorithm 557 sets a seek completion flag instep 921 and exits. Tracking can then be reacquired in tracking closealgorithm 555.

In step 922, a reference velocity is calculated. The reference velocityis greater than a minimum reference velocity by a value proportional tothe track crossing count TZC count. The sign of the reference velocityis the sign of the TZC Count. For example, a 100 track seek toward theinner diameter (ID) would initialize the TZC count with +200 (since TZCcounter counts half tracks) and the counter would decrement (assumingthe direction sensor determines that OPU 103 is moving toward the ID)for each half track crossing until reaching the destination track with acount of 0. Thus, the reference velocity would be positive for seekstoward the ID. A 100 track seek toward the OD would cause the TZCcounter to be initialized with a negative 200 value. The counter wouldincrement (assuming the direction sensor determines that OPU 103 ismoving toward the OD) until reaching 0 at the destination track. Thereference velocity has a negative sign for seeks toward the OD.

In step 923, the reference velocity calculated in step 922 is comparedwith a maximum reference velocity and, if the maximum reference velocityis exceeded, then the reference velocity is reset to the maximumreference velocity in step 924. In step 806, the actual velocity of OPU103 is calculated. The actual velocity (FbVEL) is proportional to thereciprocal of the TZC period variable, which is calculated in block 803of FIG. 8A. Step 807, then, calculates the velocity error as thedifference between the reference velocity and the actual velocity.Algorithm 557 then proceeds to step 934.

In step 934, algorithm 557 checks for the first change in sign of thevelocity error signal. If the sign of the velocity error has not yetchanged since the start of seek, then the seek acceleration phasecontinues. If the first change in the velocity error sign is detected,then the acceleration flag is cleared in step 935. During the initialphase of the seek (a.k.a. acceleration phase), the velocity of OPU 103must be accelerated until it's velocity reaches the reference velocity.Until then, the velocity error can be large. It is desirable to notallow multi-track seek control compensator's integrator, which includessummer 813, from operating during the initial phase of seek because itwill integrate this large velocity error resulting in a significantfeedback velocity overshoot of the reference velocity. In addition, thecontrol effort during this acceleration phase of a multi-track seekoperation is clamped by clamp 808 to avoid accelerating too fast whichcould also cause significant overshoot of the reference velocity.Otherwise, algorithm 557 sets the seek control effort proportionally tothe seek control variable in step 815. Algorithm 557 then proceeds tostep 804 where tracking phase lead 550 can be updated to properlyinitialize it's states in order to reduce the time required to reacquiretracking in close tracking algorithm 555. From step 935, algorithm 557proceeds to step 927.

In step 927, if OPU 103 is accelerating, then a seek control variable isset to the velocity error in step 928. In step 929, the seek controlvariable is compared with a maximum acceleration variable and, if themaximum acceleration variable is exceeded, then seek control is set tomaximum acceleration in step 930. If not exceeded, then algorithm 930proceeds to step 934.

If step 927 determines that there is no acceleration, then algorithm 557proceeds to step 931. If the velocity error is greater than a maximumvelocity error, and there has not been too many successive corrections,then algorithm 557 proceeds to step 933, which sets the seek controlvariable to be a constant times the velocity error plus a valueproportional to an integral of the velocity error, as shown in FIG. 8Aas steps 809, 813, 810, 811, and 812. If the maximum velocity error isnot exceeded in step 931, then velocity error is set to 0 in step 932and seek control is set to a value proportional to the velocity errorintegral in step 933. Algorithm 557 then proceeds to step 815.

In some embodiments, completing a seek operation in algorithm 557 alsobegins a time limited tracking loop high gain mode, which can bereferred to as a “retro rocket.” Seek completion detector 816 can enableretro-rocket gain 830 The tracking servo phase lead compensator 550(FIG. 5A) states know about the tracking and velocity error at theinstant of the seek to tracking transition as a result of properlyinitializing the phase lead compensator. Therefore, tracking servo 502knows whether to accelerate or decelerate for capturing the destinationtrack center. By significantly increasing the tracking loop gain(bandwidth) for a predetermined number of servo samples (for example 5),tracking servo 502 can more aggressively acquire the destination track.Time constraining the duration of the increased tracking loop gain canprevent the instabilities caused by mechanical resonances from growingunbounded and thus destabilizing the system. The net effect of applyingthe retro-rockets is a very aggressive closed loop track captureconverged upon track center quickly followed by a nominal bandwidth verystable tracking control system closed on the destination track.

In some embodiments, algorithm 557 is executed as part of a control loopon DSP 416. In those embodiments, seek algorithms may be executed, forexample, every 20 μs (i.e., 50 kHz). However, as more fully discussedbelow, detector signals A, B, C, D, E, and F are available every 10 μs,or at 100 kHz. In some embodiments, algorithm 557 may be solely operatedon DSP 416 so that the full 100 kHz availability of data is available.

FIG. 10B shows a block diagram of a one-track jump algorithm 559. FIG.10A illustrates the TES, tracking control effort, FES, and focus controleffort during a one-track jump algorithm. The TES and FES signals shownare the output signals from summer 506. The TES and FES signals shown inFIG. 10B are measured scope traces from output pwm's 474, who's outputsignals are centered about reference voltages, e.g. from block 462 (FIG.4). As shown in FIG. 10A, a one-track jump algorithm starts in atracking mode 1001 and includes an acceleration period 1002, a coastperiod 1003, and a deceleration period 1004. Once deceleration period1004 is complete, a settling period 1008 is followed by a focus on 1005and a tracking integrator on 1006. At which time, a tracking and focusperiod 1007 is initiated.

In FIG. 10A, during tracking period 1001 both focus servo algorithm 501and tracking servo algorithm 502 are on, therefore drive 100 is trackingand focusing on a starting track. During acceleration period 1002,one-track jump algorithm 559 applies an acceleration tracking controleffort to tracking DAC 468 which accelerates OPU 103 in the desiredtracking direction for a fixed time. During coast period 1003, one-trackjump algorithm 559 holds the tracking control effort at the levelapplied before the one track jump algorithm begins. In some embodiments,coast period 1003 is held until the TES signal output from sampleintegrity test 548 changes sign, indicating a half-track crossing.Finally, during deceleration period 1004 one-track jump algorithm 557applies a deceleration tracking control effort to tracking DAC 468. Asshown, the acceleration tracking control effort of acceleration period1002 and the coast period 1003, and the deceleration tracking controleffort of deceleration period 1004 causes TES to pass though one periodof the TES versus position curve, indicating a single track crossing. Atsome time 1006 after deceleration period 1004 ends, one-track jumpalgorithm 559 re-enables low frequency integrator 549, which wasdisabled but not reset when algorithm 559 began. Further, duringacceleration period 1002, coast period 1003, deceleration period 1004and until time 1005 after deceleration period 1004, sample and hold 530holds the focus control effort at a constant level. When one-track jumpalgorithm 559 completes, servo control algorithm 500 re-enters a mode oftracking both focus and track position.

In some embodiments, the time scale on FIG. 10A is of the order ofhundreds of microseconds so that, for example, the numbered divisionsare on the order of 200 microseconds. In some cases, one-track jumpalgorithm 559 can be executed in DSP 416 since microprocessor 432 may beunable to respond fast enough.

FIG. 10B shows schematically a block diagram of one-track jump algorithm559. Tracking compensation 1011 includes integrator 549, phase lead 550,and notch filters 551 through 553. Therefore, the output signal fromtracking compensation 1011 is the tracking control effort generatedthrough the closed tracking servo system 502 that is input tomultiplexer 558. Multiplexer 558 in FIG. 10B is represented by a switch.Track jump state machine 1010, when one track algorithm 559 isinitiated, controls multiplexer 558 so that the tracking control effortgenerated by algorithm 559 is ultimately applied to tracking actuator201 instead of the tracking control effort signal generated by trackingcompensation 1011. In FIG. 10B, the tracking control effort output fromtracking DAC 468 is input to summer 1020 which is located in powerdriver 340. As was discussed above, the tracking control effort outputfrom DAC 468 is summed with the bias control effort by summer 1020 inpower driver 340. Plant 1021 includes tracking actuator 201 as well asOPU 103 and actuator arm 104.

The tracking control effort from tracking compensation 1011 is low passfiltered in filter 1012 and input to sample and hold 1017. Duringexecution of one-track jump algorithm 559, the output signal from sampleand hold 1017 is fixed at a constant value. The constant trackingcontrol effort output from sample and hold 1017 is summed with theone-track jump tracking control profile generated in algorithm 559 atsummer 1016.

The one-track jump tracking control profile includes an accelerationpulse generated by pulse amplifier 1013 and a deceleration pulsegenerated by pulse amplifier 1014. Track jump state machine 1010controls the amplitude and duration of acceleration and decelerationpulses. Track jump state machine 1010 further controls the direction ofthe one-track jump by determining the sign of the amplitudes of theacceleration and deceleration pulses generated by pulse amplifiers 1013and 1014.

In some embodiments, the amplitude and duration of acceleration anddeceleration pulses are set during a calibration step in calibrationalgorithm 560. In some embodiments, the amplitude and duration ofacceleration and deceleration pulses may change as a function ofposition of OPU 103 over optical media 102. Further, although in FIG.10B, the jump control effort profile is shown as including a positiveand negative square wave pulse, in some embodiments acceleration pulseand deceleration pulse may include sinusoidal wave pulses in order toavoid exciting mechanical resonances in actuator arm 104.

Track jump state machine 1010, then, first latches sample and hold 1017,shuts off low frequency integrator 549, and latches sample and hold 530,then applies the acceleration pulse from pulse amplifier 1013. Statemachine 101 then monitors the TES′ signal for a sign change. When thesign change is detected, state machine 1010 applies the decelerationpulse generated by pulse amplifier 1014. If a sign change is notdetected within a set period of time, then track jump state machine 1010indicates a failed jump condition. In those circumstances, errorrecovery routines (See System Architecture disclosures) will recoverfrom this condition.

Once the deceleration pulse has ended, state machine 1010 switchesmultiplexer 558 to receive tracking control efforts from trackingcompensation 1011, and delays for a period of time to allow transienteffects to decay. State machine 1010 then turns focus back on (bysetting multiplexer 531 to accept the focus control effort rather thanthe output signal from sample and hold 530) and re-enables integrator549.

In some embodiments, one-track jump algorithm 559 shown in FIG. 10B, forexample, can further include notch filters 551 and 553 for receiving theone-track jump control effort profile output from summer 1016. Further,as is shown and discussed further below, algorithm 559 can be executedon DSP 416 in a timer interrupt mode. In some embodiments, one trackalgorithm 559 initiates phase lead 550 so that phase lead 550 isinitiated to the proper state when tracking is closed following theone-track jump operation. Initializing phase lead 550 improves dynamicresponse during the close tracking operation. Further, during aone-track jump algorithm, the focus control signal can be set to theoutput of sample and hold 530, which holds the output signal fromlow-pass filter 529 during the one-track jump operation.

FIG. 11 shows a block diagram of a DSP firmware architecture 1100according to the present invention. As discussed above, microprocessor432 and DSP 416 can communicate through mailboxes 434. Initializationblock 1101, main loop block 1102, timer interrupt block 1103, and sensorinterrupt block 1120 represent algorithms executing on DSP 416. Ininitialization 1101, all of the filter states in FIGS. 5A and 5B are setto zero and all initializations are accomplished. Main loop 1102represents an infinite loop that actually does nothing, since in mostembodiments DSP 416 is interrupt driven. Timer interrupt 1103 executesone-track jump algorithm 559.

Focus and tracking servo algorithms are executed as part of sensorinterrupt 1120. Sensor interrupt 1120 is available when all of thedetector sensor signals A, B, C, D, E and F are available at decimationfilters 414-1 and 414-6 (FIG. 4). Therefore, in some embodiments (forexample), there is a sensor interrupt at a frequency of 100 kHzfrequency, which occurs every 10 μs. Therefore, every 10 μs DSP 416receives a sensor interrupt which initiates sensor interrupt code 1120shown in FIG. 11.

In step 1104, algorithm 1120 determines which algorithm to execute,focus or tracking. Focus servo algorithm 501 and tracking servoalgorithm 502 alternate, therefore each is executed every 20 μs.Therefore, focus and tracking loops are sampled at 20 μs or 50 kHzrather than interrupting every 20 μs and executing both focus andtracking algorithms. In this fashion, there is a lower time delaybetween sampling detector signals A, B, C, D, E, and F. In someembodiments, a third loop in algorithm 1120 can execute a spin-motorservo algorithm (see the Spin Motor Servo System disclosures). However,DSP 416 operates very fast but has limited resources in terms of memory.

If algorithm 1120 executes focus servo algorithm 501, then an FES′signal is calculated in step 1111. The FES′ signal is the output signalfrom sample integrity test 515, therefore step 1111 includes focus servoalgorithm 501 through integrity test 515. In some embodiments, defectdetection algorithm 591 can then be calculated, providing a defectsignal to a write abort algorithm which may be operating onmicroprocessor 432.

When the FES′ signal is calculated in step 1111, algorithm 1120 proceedsto step 1112. In step 1112, algorithm 1120 determines if focus is on. Insome embodiments, algorithm 1120 determines that focus is on or off bychecking a bit flag in a control word held in mailboxes 434. If focus isoff, then algorithm 1120 is finished with the focus operation andproceeds to step 1114. If focus is on, the algorithm 1120 finishes theoperations of focus servo algorithm 501 in step 1113. After step 1113,then algorithm 1120 proceeds to step 1114.

If tracking servo algorithm 502 is chosen in step 1104, then algorithm1120 proceeds to step 1105. In step 1105, tracking servo algorithm 502through TES sample integrity test 548 is executed to calculate a TES′value. Algorithm 1120 then proceeds to step 1106. In step 1106,algorithm 1120 determines if a seek operation is being undertaken, insome embodiments by checking a seek flag set in a control word held inmailboxes 434.

If a seek operation is being undertaken, then algorithm 1120 proceeds toseek algorithm 557 in step 1107. Step 1107 can perform many of the stepsdescribed with FIGS. 8A, 8B, 9A and 9B describing seek algorithm 557.Additionally, some of the steps shown in FIGS. 9A and 9B can beperformed through tasks in multiplexer 1116, as described below. Forexample, seek initialization 901 can be performed as tasks inmultiplexer 1116.

If there is no current seek operation, or when step 1107 is completed,algorithm 1120 proceeds to step 1108. In step 1108 algorithm 1120determines whether tracking is on or not. If tracking is on, thenalgorithm 1120 proceeds to step 1109 where the remaining portion oftrack servo algorithm 502 is executed. If tracking is off, or when step1109 is completed, algorithm 1120 proceeds to step 1110. Usually,algorithm 1120 either executes step 1107, step 1109, or neither.However, in some cases a seek operation may finish in step 1107 and thentracking should be turned on in step 1109, in which case both steps 1107and 1109 are executed during the same interrupt.

In step 1110, minimum and maximum calculations on any variable can becalculated. The particular variable can be chosen by microprocessorthrough mailboxes 434. Step 1110 allows variables to be monitored andtrace data to be kept for calibration routines or monitoring routines.From step 1110, algorithm 1120 proceeds to step 1114.

In step 1114, algorithm 1120 determines if the drive is in the coastmode of a one-track jump. If step 1114 indicates a coast mode of aone-track jump, which in some embodiments can be determined by checkingthe appropriate bit flag in a control register of mailboxes 434, thenalgorithm 1120 proceeds to step 1115. Step 1115 determines if thedeceleration step of the one-track jump should be started and, if so,starts the deceleration step. Once step 1115 is complete, or if step1114 determines that there is no one-track jump operation, thenalgorithm 1120 proceeds to multiplexer 1116.

One track jump algorithm 559, as discussed with FIGS. 10A and 10B,execute in a timer interrupt mode. However, algorithm 1120 operatesevery 10 microseconds, which allows steps 1114 and 1115 to execute every10 microseconds, in embodiments operating at a frequency of 100 kHz. Thetimer interrupt from one track jump algorithm 559 has a lower interruptpriority than sensor interrupts that trigger algorithm 1120. Sensorinterrupt allows step 1114 to start deceleration in step 1115.

Multiplexer 1116 includes tasks that can be done after either thetracking loop or the focus loop processing is completed if any of theexecution time is available before the next sensor interrupt. Typically,the tasks included in multiplexer 1116 can be tasks that do not need tobe serviced as frequently as do focus and tracking algorithms. Forexample, one task that can fall into multiplexer 1116 is TES OK 517. Asdiscussed before, TES OK 517 checks the FES signal and, if the FESsignal is too high, determines that the TES signal is unreliable.However, tracking servo algorithm 502 does not need to be immediatelyshut down, so the TES OK task can wait until its turn in multiplexer1116. In some embodiments, multiplexer 1116 can include 16 tasks.Another example of a task that can be included in multiplexer 116include reading new variables from mailboxes 434 and updating variablesused in other areas of algorithm 1120. In that fashion, ifmicroprocessor 432 adjusts a gain or offset value utilized in focusservo algorithm 501 or tracking servo algorithm 502, then a task inmultiplexer 1116 can read that gain or offset and update the appropriatevariables. Some tasks that may be executed in multiplexer 1116 includefocus loop OK algorithm 536, turn focus off algorithm (when commanded todo so), clear focus bad flag, zero the states of low frequencyintegrator 549, move the TES and FES gain and offset variables frommailboxes to internal variables, zero the low pass filter states ofskate detector 561 if skate detector 561 is disabled, close trackingalgorithm 555, initialize one-track jump algorithm 559, reset the jumpstatus, initialize the seek variables of multi-track seek algorithm 557and begin the seek, reset the seek status, clear write-abort status ofwrite abort algorithm 537, seek length spiral compensation in algorithm557, calibrate notch filter coefficients of notch calibration algorithms520 and 552, provide general purpose mailbox communications.

From multiplexer 1116, algorithm 1120 proceeds to update status mailbox1117, which writes status bits to mailboxes 434 as required. Forexample, error interrupts to microprocessor 432 can be set at step 1117.Algorithm 1120 then proceeds to step 1118 where diagnostic data can bemaintained.

In some instances, algorithm 1120 may take more time to complete onecycle than there is time between sensor interrupts. In that case, somesensor interrupts may be missed. However, if too many interrupts aremissed or if there is not enough idle time between interrupts, there canbe instabilities developed in some embodiments.

Example Embodiments of Calibration Algorithms

In some embodiments, dynamic calibrations can be performed on componentsof drive 100 in order to dynamically optimize operation of drive 100.Several calibration algorithms have been mentioned in the precedingdiscussion on signal processing, including the following calibrations:detector offset calibration 548 (FIG. 5A) and detector gain calibration583 (FIG. 5A), which calibrates the offset and gain parameters foroffsets 402-1 through 402-6 (FIG. 4) and amplifiers 404-1 through 404-6(FIG. 4), respectively; FES offset calibration 508 for calibrating theFES offset applied to summer 507 (FIG. 5); FES gain calibration 510 forcalibrating FES gain amplifier 509 (FIG. 5); inverse non-linearitycalibration 512 which calibrates inverse non-linearity algorithm 511(FIG. 5); TES-to-FES cross-coupling gain calibration 579 for calibratingTES-to-FES cross-coupling gain 514, which cancels at least partiallyTES-to-FES cross coupling in the FES signal; notch calibration 520 forcalibration of notch filter 519; focus loop gain calibration 522 forcalibrating the loop gain of focus servo algorithm 501; calibratedfeed-forward gain 532; TES offset calibration 542 for setting the TESoffset applied in summer 541; TES Gain calibration 544 which set thegain of gain 543; inverse nonlinearity calibration 547 which calibratesinverse nonlinearity algorithm 546; notch calibration 552 whichcalibrates notch filter 551; calibration algorithm 560 which calibratesone-track jump algorithm 559; loop gain calibration 562 for calibratingTES servo algorithm 502; and calibrated feed-forward algorithm 579. Insome embodiments of the invention, further calibrations can be added.For example, low frequency integrators 516 and 549 may be calibrated.

FIG. 12A shows a block diagram of an example calibration life-time fordrive 100. As indicated by state 1201, many calibrations within drive100 are set, or at least initially set, when drive 100 is fabricated.These settings can, for example, include initial values for controllingpower supplies or for calibrating motor servo parameters. FIG. 12B showsa chart of an example of several operating parameters and when thoseparameters can be calibrated and at what stage in calibration thoseparameters are calibrated. Initial default values for tracking and focusservo system parameters can also be initialized during initial drivecalibration 1201. For example, offset and gain values from detectoroffset calibration 584 and detector gain calibration 583, notch filtercalibrations 520, and notch filter calibration 552 can be set at thistime. In operation, calibration algorithm 1201 can load default valuesfor each of the calibration parameters and adjust them for theparticular characteristics of drive 100 operating with a standardizedoptical media 102.

Once the particular factory calibration parameters are determined ininitial calibration 1201, then in some embodiments factory calibrationvalues can be stored in program memory 330, which can include a flashmemory. In some embodiments, media specific calibration parameters,which can, for example, include detector input parameters to detectoroffsets 402-1 through 402-6 and gains 404-1 through 404-6, FES offsetfrom calibration 508, TES offset from calibration 542, FES gain fromcalibration 510, TES gain from calibration 544, focus loop gainparameters from loop gain 522, tracking loop gain parameters from TESloop gain 562, calibration parameters for inverse non-linearityfunctions algorithms 511 and 546 (FES inverse non-linearity parametersand TES inverse non-linearity parameters, respectively), notch filterparameters for notch filters 519 and 551, and one track jumpcalibrations 560, can be written onto optical media 102 so that, whendrive 100 “wakes up” with a particular optical media, the best operatingparameters for optical media 102 can be read and utilized. In someembodiments, the best average operating parameters can be stored inprogram memory 330 and drive 100 can start with those parameters. Theaverage parameters stored in program memory can be updated each timedrive 100 is calibrated.

Initial calibration 1201 can also be repeated during a rework or repaircalibration 1202. Calibration 1201, then, can be repeated when drive 100is, for some reason, returned for repair.

Calibration cycle 1203 represents normal, in-service, calibrations fordrive 100. Calibration 1203 can be executed, for example, whenever a newoptical media 102 is loaded, when drive 100 is started, and during anerror recovery algorithm (see the Microcode System Architecturedisclosures). In some embodiments, when drive 100 is initially started(i.e., “wakes up”), cycle 1203 receives default values for calibrationparameters from flash memory 330. In some embodiments, media specificcalibration parameters can be read from optical media 102. In someembodiments, default values for drive specific and media specificparameters can be stored in program memory 330 (FIG. 3) and loaded whendrive 100 is powered. In some embodiments, temporary media specificparameters can be stored in memory 330 so that, when drive 100 isre-started, the preceding parameters can be utilized. Since drive 100may often be started with the same optical media as when it was shutdown, stored parameters can save time in “waking-up” drive 100.

In some embodiments, default parameters may be changed over time. Asdrive 100 ages, many of the default parameters can become very differentfrom the initial calibration parameters required to operate drive 100.Therefore, in some embodiments of drive 100, the actual drive parametersmay be re-stored as default parameters. In some embodiments, an averageof the actual drive parameters with the default parameters may bere-stored as default parameters. However, if drive 100 is operated inextreme environments or if optical media 102 is particularly problematic(e.g., if optical media 102 is severely not flat due to exposure to heator other warping environments), then the actual parameters required tooperate under those conditions should not replace or alter the currentdefault parameters. Therefore, in some embodiments if the currentparameters vary beyond threshold values from the default parameters, thedefault parameters are not replaced or altered by these parameters.

FIG. 12B shows drive specific parameters which are calibrated. Ingeneral, as discussed above, optical media 102 can have a pre-masteredportion (which is read only) and a writable portion (which isread/write). In general, operating parameters are calibrated foroperation of drive 100 under all of these conditions, i.e. readoperation over the writable portion of optical disk 102, write operationover the writable portion of optical disk 102, and read operation overthe pre-mastered portion of optical disk 102.

FIG. 13A shows an embodiment of a calibration sequence 1350 forcalibrating over each media type of an optical media 102 and for readand write, where appropriate, modes over those media types. In general,optical media 102 can have several media types and several regions withdiffering media types.

Sequence 1350 starts with step 1351 where a first set of conditions isset. For example, the first set of conditions can be a read mode over apre-mastered portion of optical media 102. In step 1352, preamplifier310 (FIG. 3A) is set for the correct mode (e.g., read or write). In step1353, laser power to laser servo 105 is set to the appropriate power forthat mode. In step 1354, OPU 103 is positioned over the selected mediatype (e.g., pre-mastered or writable). In step 1301, a calibrationalgorithm 1301 is executed. Calibration algorithm 1301 executes asequence of calibration routines that are appropriate for the selectedmode and selected media type and stores the operating parameters for usein disk drive 100. In step 1355, sequence 1350 checks to determine ifall combinations of operating modes and media types have beencalibrated. If there are more combinations, then sequence 1350 proceedsto step 1357 where the next combination of operating mode and media typeis selected. From step 1357, sequence 1350 proceeds to step 1352 tocalibrate the next combination. When all combinations are calibrated,algorithm 1350 finishes at step 1356.

FIG. 13B shows an embodiment of an example calibration routine 1301which can be executed either during initial drive state 1201 or reworkstate 1202. Calibration routine 1301 shown in FIG. 13B, for example,would be appropriate for a read mode calibration of pre-mastered media.In some embodiments, as illustrated in state 1203, calibration algorithm1301 can be executed whenever drive 100 is started-up or whenever a newoptical media 102 is inserted into drive 100. When algorithm 1301 isinitiated in step 1302, algorithm 1301 reads default calibrationparameters from program memory 330 (FIG. 3). Algorithm 1301 thenproceeds to step 1303.

In step 1303, algorithm 1301 executes detector offset calibrationalgorithm 584 and detector gain calibration 583 in order to calibrateoffsets 401-1 through 401-6 and amplifiers 404-1 through 404-6 tooptimally receive detector signals A_(R), B_(R), C_(R), D_(R), E_(R) andF_(R). Once OPU input parameters Offset and Gain are calibrated, spinmotor 101 can bring optical media 102 to a starting rotational speed atwhich point algorithm 1301 proceeds to step 1304.

In step 1304, algorithm 1301 executes FES Gain calibration 510 tocalibrate the FES Gain parameter to gain amplifier 509. At this point,focus loop 501 can be closed and algorithm 1301 then proceeds to step1305 where algorithm 1301 executes FES offset calibration 508,optimizing the FES Offset parameter to summer 507. Algorithm 1301 thenproceeds to step 1306 where algorithm 1301 executes TES offsetcalibration 542. Algorithm 1301 then executes TES gain calibration 544in step 1307. Algorithm 1301 then executes TES offset calibration 542again in step 1308. In some embodiments, TES offset calibration 542 andTES gain calibration 544 may alternately be executed until the values ofthe TES offset and the TES gain acceptably converge. Further, in someembodiments FES gain calibration 510 and FES offset calibration 508 maybe alternately executed until the FES gain parameter and the FES offsetparameters converge.

In the embodiment of algorithm 1301 shown in FIG. 13B, once the TESoffset parameter has been re-calibrated in step 1308, algorithm 1301proceeds to step 1309 to execute focus loop-gain calibration 522.Tracking loop 502 is closed before algorithm 1301 executes trackingloop-gain calibration 585 in step 1310. Algorithm 1301 then proceeds tostep 1311, where TES/FES crosstalk gain calibration 579 is executed.Once TES/FES crosstalk gain calibration 579 is executed, algorithm 1301then executes focus loop gain calibration 522 in step 1312 and trackingloop gain calibration 585 in step 1313. In some embodiments, trackingloop gain calibration 585, focus loop gain calibration 522, and TES/FEScrosstalk gain calibration 579 can be sequentially executed until thecalibration parameters converge.

In step 1314, algorithm 1301 calibrates notch filters 519 and 551 byexecuting notch calibration 520 and notch calibration 552. Again, insome embodiments of the invention, algorithm 1301 may proceed againthrough steps 1303 through 1314 until all of the resulting calibrationparameters have converged.

In step 1315, algorithm 1301 loads the new calibration parameters intoprogram memory 330. In some embodiments, program memory 330 is a flashmemory. In some embodiments, the new parameters may be written ontooptical media 102 so that optical media 102 can be started each timewith these optimized parameters. Again, in some embodiments if the newcalibration parameters (operating parameters) of drive 100 differ beyonda threshold value from the old operating parameters, then the newcalibration parameters may not be stored or may not be stored to replacethe old operating parameters (the stored parameters). New calibrationparameters that vary significantly from the old operating parameters maybe stored until a new calibration operation is performed and, if the newcalibration parameters from the new calibration operation also varysignificantly, then the new calibration parameters may be stored. Insome embodiments, an average of the new calibration parameters and theold calibration parameters can be stored in order that operatingparameters not vary to quickly. In some embodiments, operatingparameters may be allowed to vary by a maximum amount so that if the newcalibration parameters differ from the old operating parameters by anamount over the maximum amount, than the old operating parameters variedby the maximum amount are stored in place of the new calibrationparameters. In some embodiments, the new calibration parameters arestored in a flash memory of program memory 330. In some embodiments,some of the operating parameters can be written onto optical media 102instead. Writing operating parameters onto optical media 102 directlycan be useful for storing parameters that closely depend on theparticular optical media.

In some embodiments of the invention, further calibrations may also beexecuted in algorithm 1301, including calibration 560 for calibratingone-track jump algorithm 559, inverse non-linearity calibrations 512 and547, and calibrations related to decimation filters 414-1 through 414-6.

FIGS. 14A and 14B show embodiments of step 1302 of FIG. 13. Algorithm1302 calibrates OPU input parameters A, B, C, D, E and F by setting theoffset values of each of offsets 402-1 through 402-6 and the gain valuesof each of variable amplifiers 404-1 through 404-6. In some embodiments,step 1302 may include a calibration of decimation filters 414-1 through414-6 as well. The embodiment shown in FIG. 14A performs a dark-currentcalibration of the OPU input parameters. The embodiment shown in FIG.14B performs a calibration of the OPU input parameters with lightscattering present.

The embodiment of step 1303 shown in FIG. 14A starts with step 1401where parameters can be passed to step 1303. In some embodiments, theparameters include a gain parameter bFrontEndGain and a calibration typeflag bCalTypeFlag. The gain parameters indicate the gains of each ofamplifiers 404-1 through 404-6. Algorithm 1303, then, includes aspectsof detector offset calibration 584 and detector gain calibration 583.

In some embodiments, the gains and offsets of gains 404-1 through 404-6and offsets 402-1 through 402-6 can be performed with laser off, i.e. adark-current calibration. In some embodiments, the gains and offsets ofgains 404-1 through 404-6 and offsets 402-1 through 402-6 can beperformed with laser on and without optical media 102 in order to adjustfor the presence of light scattering in OPU 103. FIG. 14A illustrates adark current calibration. FIG. 14B illustrates an adjustment tocalibrate for light scattering.

In some embodiments, as shown in FIG. 14A, the gain of variableamplifiers 404-1 through 404-6 is fixed while the offset values ofoffsets 402-1 through 402-6 are calibrated. In some other embodiments,the gain of amplifiers 404-1 through 404-6 can also be adjustedaccording to a calibration criteria (for example that the dynamic rangeof the outputs from decimation filters 414-1 through 414-6 should be afixed peak-to-peak value).

In step 1402, algorithm 1302 switches to a high power mode. In highpower mode drive 100 is operational, as opposed to sleep mode. Operatingvoltages are brought to their operating values and power is available tolaser 218 of OPU 103 and spin motor 101.

From step 1402, algorithm 1302 executes step 1404. In step 1404,algorithm 1302 determines the gains of each of amplifiers 404-1 through404-6 based on the gain parameter input at step 1401, bFrontEndGain. Insome embodiments, the gain of each of amplifiers 404-1 through 404-6 isset to bFrontEndGain. The value of the gains for each of amplifiers404-1 through 404-6 can be stored in a gain array 1414. In someembodiments, the parameter bFrontEndGain may include a different gainvalue for each of amplifiers 404-1 through 404-6. The gain parameters,then, can be set during a factory calibration or a re-work calibrationand stored in program memory 330. In some embodiments, the gain valuesfor each of amplifiers 404-1 through 404-6 are set to fill the operatingrange of digital to analog converters 410-1 and 410-2 (FIG. 4).

In step 1405 the laser is set on or off depending on the bCalTypeFlagparameter input during step 1401. If the laser is off, then thecalibration is a dark current calibration, zeroing the output ofdecimators 414-1 through 414-6 when the laser power is off. Acalibration with laser 218 on can further eliminate systematic lightscattering in OPU 103.

In steps 1406 through 1411, the offset values for each of offsets 402-1through 402-6 is set. In some embodiments, the offset value is set sothat the output signal from decimators 414-1 through 414-6 is zeroduring calibration. In a laser-on calibration, steps 1406 through 1411can, in some embodiments, be executed with a standard optical media 102in drive 100 to provide standard reflections. In some embodiments, nooptical media 102 is utilized or a light absorbing material insubstitution for optical media 102 can be utilized. Each of blocks 1406through 1411 updates part of an offset array 1415, which stores theoffset values for offsets 402-1 through 402-6. Algorithm 1303 then exitsin step 1413, indicating any error conditions that have occurred (suchas offset values out of range, laser failed to function, or command wasaborted, for example).

FIG. 14B shows an embodiment of an input signal offset and gaincalibration algorithm according to the present invention that includesoffsets for stray light. Detectors 225 and 226 (FIG. 2B) of OPU 103, forexample, receive light from laser 218 that has not been reflected fromoptical media 102. This “stray light” causes sensor offsets that canaffect tracking servo system 502 and focus servo system 501 (FIGS. 5Aand 5B). One particular issue is that when the power of laser 218 isshifted from read power to write power, for example, the amount of straylight measured at detectors 225 and 226 shifts, resulting in shifts inthe tracking error signal offset and focus error signal offsets thatoptimize operation of optical disk drive 100. In some cases, the shiftcan be large enough to cause a write abort condition to be indicated bywrite abort 537 or to cause writing of data with uncontrolled trackingerror signal offsets and focus error signal offsets.

FIG. 14B shows an embodiment algorithm 1302 that calibrates input signaloffsets for read laser powers and write laser powers. Optical disk drive100, then, can automatically shift input signal offsets so as toeliminate shifts in offset due to operating changes in the power oflaser 218.

In step 1450 of algorithm 1302, optical disk drive 100 is powered fullon except that spin driver 101 is not operating. Further, optical media102 is removed from optical disk drive 100 so that no light is reflectedback into OPU 103 from optical media 102. When optical disk drive 100 ispower on, all voltage levels are brought to operating parameters and thedrive is “awake” instead of in sleep mode.

In step 1451, input signal gains, e.g. the gains of each of gain adjusts404-1 through 404-6, are calibrated in read mode. In some embodiments,the input signal gains for each of the input signals, signals A_(v),B_(v), C_(v), D_(v), E_(v) and F_(v) shown in FIG. 4, is set to constantvalues. In some embodiments, the input signal gains for each of theinput signals can be set so as to fill the dynamic range ofanalog-to-digital converters 410-1 and 410-2 when the read power levelis set.

In step 1452, the input signal gains can be set for a write power levelof laser 218. Again, the input signal gains can be set to constantlevels. Further, the input signal gains can be set in order to fill thedynamic range of analog-to-digital converters 410-1 and 410-2 when thewrite power level is set.

In step 1453, a dark current input offset calibration is performed. Anembodiment of this input offset calibration is shown in FIG. 14A.

In step 1454 the laser power of laser 218 is set at read power. In someembodiments, read power is set nominally at 0.25 mW. Additionally, theinput sensor gains of gain adjustments 404-1 through 404-6 are set forread power and other channel gains and offsets in preamp 310 (FIG. 3)can be set for read operation. Further, input signal offsets of offsets402-1 through 402-6 can be zeroed. In step 1455, digitized values of theinput signals (e.g., A_(f), B_(f), C_(f), D_(f), E_(f) and F_(f) in FIG.4) are measured. In some embodiments, the digitized values of the inputsignals are averaged over multiple samples after a time delay fromsetting the power level of laser 218. For example, the time delay can beabout 10 msec. Additionally, 256 samples of each of the digitized inputsignals can be acquired and averaged to determine the stray lightvalues. Input signal offsets for read power levels, then, can be set tovalues such that the digitized input signals are a predetermined value,for example zero.

In step 1456, laser power and other channel parameters (e.g., inputsignal gains and parameters of preamp 310) are set for write mode. Insome embodiments, write laser power is nominally at about 1.1 mW. Insome embodiments, write laser power can be set at about 1.5 times readpower and input signal offsets for any other laser power can beinterpolated from the input signal offsets at these values. In somecases, the measured stray light is substantially linear with laserpower.

In step 1457, the input signal offsets for write power are measured. Theinput signal offsets of offset blocks 402-1 through 402-6 can be zeroedand the digitized values of the input signals are measured. The inputsignal offsets appropriate for write operations are set such that thedigitized values are at a predetermined value, for example zero. Again,a time delay, for example of about 10 ms, can be executed beforemeasurement of the digitized values. Again, an average of the digitizedinput signals over many samples, for example 256, can be utilized to setthe input signal offsets.

In some embodiments, the read power level can be set nominally to 0.25mW and the write power level is nominally 1.1 mW. In some embodiments,two points are utilized in calibration, e.g. the read power level and1.5 times the read power level, and read and write offsets areinterpolated from these points.

Input signal offset values for no laser power (dark current), readpowers, and write power can then be stored, for example in memories 320and 330 (FIG. 3). During operation of optical disk drive 100, inputsignal offsets appropriate for read operations are loaded when opticaldisk drive 100 is in read mode and input signal offsets appropriate forwrite operations are loaded when optical disk drive 100 is in writemode. In some embodiments, if other laser powers are set (for example, areduced laser power during multi-track seek operations) appropriateinput signal offsets can be determined by linear interpolations usingthe input signal offsets at read power and at write power. Whenswitching between read mode and write mode, the appropriate input signalparameters can be set in order to minimize transients in focus servosystem 501 and tracking servo system 502.

Frequent calibration of the dark current offset can correct for thermaldrift of the analog electronics of drive 100. For example, offsetcalibration 1302 of FIG. 14A can be performed whenever focus is closed.A method of calibration for thermal drift can include opening trackingand focus servos and shutting laser power off, measuring the darkcurrent offsets by monitoring the digitized values output from analog todigital converters 410-1 and 410-2 or decimators 414-1 through 414-6,and adjusting the stray light values for each of a read mode (i.e., withoperating parameters set for read operations) and a write mode (i.e.,with operating parameters set for write operations). Once the straylight values have been adjusted for the new dark current offset values,focus and tracking can be reacquired. In some embodiments, average darkcurrent offsets can be measured. In some embodiments, detector inputscan be disabled and dark current samples can be read while tracking andfocus servo systems remain closed.

The write power stray light values can be measured during manufacturingat one know laser power, for example 1.1 mW. In some embodiments, anadaptive calibration is performed to adjust the laser power to optimizewrite error rates. The actual write power during operation of drive 100,then, will vary. A stray light adjustment algorithm scales the straylight correction values based on the actual write laser power using alinear interpolation. These scaled write stray light values are added tothe periodically measured dark offset values and stored whenever thedark offset values are measured. In write mode disk 100 utilizes thewrite values and in read mode disk 100 utilizes the read values. Inputoffsets, then, are always accurate for the laser power being used andtransients in tracking servo system 502 and focus servo system 501 canbe minimized. If stray light is not considered in the input offset,tracking servo system 502 and focus servo system 501 will experienceshifts when laser power changes. With stray light offset calibration, alooser tolerance for stray light can be accommodated.

FIGS. 15A and 15B illustrate an embodiment of focus gain calibration510, which can be executed in step 1304 of calibration algorithm 1301 ofFIG. 13. FIGS. 15A and 15B also illustrate calibration of a focus sumthreshold value. FIG. 15A shows a block diagram of algorithm 510 whileFIG. 15B illustrates graphically signals and actuator motions initiatedby focus gain calibration 510. In step 1501, algorithm 510 is called. Instep 1502, default values for the FES gain of FES gain 509 and the FESoffset of offset summer 507 are loaded. As was discussed above, thestarting FES offset and FES gain parameters can be input from opticalmedia 102 in some embodiments and, in some embodiments, can be inputfrom program memory 330.

In step 1503, algorithm 510 generates a focus control effort that movesOPU 103 sinusoidally from its present position to an extreme point ofOPU 103. The extreme point is the point furthest away or the pointclosest to optical media 102. This step is graphically illustrated inthe actuator position graph during time period 1. From the extreme pointof OPU 103, OPU 103 is sinusoidally moved to the opposite extreme andback to the extreme point in step 1504, as is indicated in time period 2in FIG. 15B. During this movement, the sum signal from summer 534 ismonitored. An example of the sum signal from summer 534 is shown in FIG.15B on the same time axis as is the actuator position signal. The peakvalues of the sum signal are also determined in step 1504. In someembodiments, the peak value of the sum signal is the average of the twopeak values measured as OPU 103 is moved from the first extreme positionto the opposite extreme position and back to the first extreme position.The peak sum signal and the sum of peak sum signals can be stored invariables 1507, along with a counter for the number of peak valuesstored.

In step 1505 of algorithm 510, a reasonable sum threshold is calculated.The reasonable sum threshold is set based on the peak sum signalcalculated in step 1504. In some embodiments, the reasonable sumthreshold is set to be half of the peak sum signal calculated in step1504. However, any reasonable value can be utilized for the reasonablesum threshold (such as, for example, between about 30% to about 90% ofthe peak sum signal). As the reasonable sum threshold is lowered thefocus control becomes more lax. Conversely, as the reasonable sumthreshold is increased it becomes increasingly easier to lose focus. Thereasonable sum threshold is output to focus OK algorithm 536 and isfurther utilized to determine whether there is sufficient focus toindicate a focus closed condition to other algorithms executing on drive100.

From step 1505, algorithm 510 proceeds to step 1506. In step 1506,algorithm 510 moves OPU 103 from the first extreme to the oppositeextreme and measures a focus control effort FCSOFFA that occurs at thethreshold indicated by the reasonable sum threshold value calculated instep 1505. Further, another sum threshold peak is measured to be addedto the sum peak variables 1507. In step 1508, algorithm 510 moves OPU103 back to the extreme position and measures a focus control effortFCSOFFB as the sum signal again crosses the threshold indicated by thereasonable sum threshold value. Again, the sum signal peak is tabulatedand recorded in variables 1507. A threshold in-focus control effort, theoffset control effort FCSOFF, then, can be calculated as the average ofthe two threshold control efforts FCSOFFA and FCSOFFB. The movement ofOPU 103 and the resulting sum signals as steps 1506 and 1508 areexecuted as is shown in FIG. 15B at times 3 and 4, respectively.

In some embodiments of algorithm 510, in particular those embodimentsthat are executed on microprocessor 432, algorithm 510 controls OPU 103through DSP 416. In step 1509, algorithm 510 from microprocessor 432communicates the threshold value to DSP 416. DSP 416 then monitors thesum signal from summer 507 and compares the sum signal to the calibratedthreshold value to determine, for example, if focus is bad (e.g.,algorithm 536), if focus can be closed (e.g., algorithm 535), or if adefect is detected (e.g., algorithm 591).

In step 1510, algorithm 510 moves OPU 103 to the position indicated bythe focus offset control effort FCSOFF calculated in step 1508. In someembodiments, OPU 103 is moved to FCSOFF in a sinusoidal fashion in orderto avoid exciting mechanical resonances which can be excited withmotions of OPU 103 that are not smooth.

Algorithm 510 then proceeds to step 1511. In step 1511, a smallersinusoidal perturbation around the FCSOFF control effort is applied tofocus actuator 206 in order to sinusoidally move OPU 103 about thethreshold focus position indicated by the reasonable sum threshold valueof the sum signal by a small amount (e.g., half the amplitude requiredto make the sum signal drop below the reasonable sum threshold). As OPU103 is oscillated about the threshold value, the FES signal output fromsummer is monitored. The FES signal can be sampled a number of times(e.g., 300 times) at each point and the FES peak maximum and FES peakminimum values can be stored in variables 1512. In some embodiments,step 1511 monitors the FES signal through four oscillations of OPU 103,however any number of oscillations can be monitored. FIG. 15B shows intime period 6 the sinusoidal movement of OPU 103 and the FES signal.

In step 1513, the average maximum value of the FES signal and theaverage minimum value of the FES signal through the oscillationsexecuted in step 1511 are calculated from variables 1512. Additionally,the average peak-to-peak value of the FES signal is calculated in step1513. Additionally, in some embodiments peak sum signals are added toprevious peak sum signals and a running total is stored.

In step 1514, a new gain value is calculated from the values obtainedfrom the average peak-to-peak value of the FES signal calculated in step1513. In some embodiments, the gain is calculated so that the averagepeak-to-peak value of the FES signal is a predetermined value. In someembodiments, the gain is calculated so that the maximum and minimumpeak-to-peak values are at a predetermined value. Once the gain value iscalculated, step 1514 transfers the gain value through mailboxes 434. Insome embodiments, the calculations of steps 1513 and 1514 can beperformed by DSP 416. In some embodiments, the calculations of steps1513 and 1514 can be performed by microprocessor 432 with the FES peakvalues determined by DSP 416. In step 1514, the new gain value iswritten to mailboxes 434 for transfer to DSP 416 or to microprocessor432, depending on which of DSP 416 or microprocessor 432 performs thecalculation.

Steps 1511, 1513, and 1514 can be repeated a number of times, forexample four times, in order to converge on the best calibrated gainvalues. In step 1515, microprocessor 432 updates sensor thresholdmailboxes 1515 with a value, for example, of half the average peak sumsignal to be implemented by focus servo algorithm 501. In step 1516, thenew gain values for FES gain 509 are stored, for example in programmemory 330. In step 1517, algorithm 510 moves OPU 103 away from opticalmedia 102 before exiting algorithm 510 in step 1518.

FIGS. 16A, 16B and 17 show embodiments of FES offset calibration 508. Insome embodiments, FES offset calibration 508 optimizes the FES Offsetvalue for best servo operation, as shown in FIG. 16. In someembodiments, FES offset calibration 508 optimizes the FES Offset valuefor best read/write operation, which is shown in FIG. 17. In someembodiments, FES offset calibration 508 executes algorithm 508 shown inFIGS. 16A and 16B and algorithm 508 shown in FIG. 17 and calculates anFES offset calibration which compromises between optimum servo-systemconsideration and optimum read/write considerations. FIG. 16C shows agraph of the TES peak-to-peak signal as a function of FES offset curve.If the FES offset is enough to move off of the flat portion of thecurve, then the TES peak-to-peak signal will get smaller and the TESgain will need to change.

FIG. 16A shows an embodiment of focus offset calibration 508 thatincludes an optimum servo calibration. Algorithm 508 starts when calledat step 1601. In step 1602, algorithm 508 checks to be sure that focusservo algorithm 501 indicates that focus is closed and the spin servoindicates that optical media 102 is spinning. See the Spin Motor ServoSystem disclosures. If focus is not closed or optical media 102 is notspinning, then algorithm 508 returns after setting an error flag in step1607. If an abort condition is detected, then algorithm 508 exitsthrough step 1609 after setting an abort flag.

If both focus is closed and optical media 102 is spinning, thenalgorithm 508 proceeds to step 1603 where tracking is turned off. Whentracking is turned off, i.e. tracking servo algorithm 502 is not closed,then the TES signal becomes a sinusoidal signal as the tracks pass underOPU 103. In step 1604, the TES settings (including TES Gain and TESoffset values as well as the current tracking control signal) arestored. In step 1605, the TES gain is set to a default value (forexample 0×20) and the TES offset is set to 0. If algorithm 508 isprimarily executed on microprocessor 432, these parameters can becommunicated to DSP 416 in mailboxes 434 where DSP 416 monitors the TESsignal output from TES gain 543 during execution of algorithm 508.

In step 1606, FES offset is set to zero. In step 1608, algorithm 508monitors the peak-to-peak value of the TES signal output from TES gain543 while decrementing the focus offset value. The focus offset value isdecremented by a set amount during each step. The TES peak-to-peak valuecan be generated by TES P-P algorithm 545. During step 1608, FES offsetis decremented by a set amount and, if the TES peak-to-peak valueincreases, then a best FES offset value is set to the FES offset value.If, during a set number of decrements, the peak-to-peak TES signaldecreases, then step 1608 stops decrementing and exits. In someembodiments, if a best FES offset value is located (i.e., indicatingthat a peak in the TES peak-to-peak value versus FES offset curve hasbeen located), then algorithm 508 proceeds to step 1612. In someembodiments, once a peak in the TES peak-to-peak value is located, thefocus offset value may be stepped through the peak with a finerincrement in order to better locate the peak and provide a better valueof the focus offset value. If an error is discovered (e.g., the TESpeak-to-peak value is below a threshold peak-to-peak value) thenalgorithm 508 can exit with an error-flag set at step 1607. If an abortcommand is received, algorithm 508 can exit with an abort indication instep 1609.

In some embodiments, or if a peak in the TES peak-to-peak curve has notbeen located, algorithm 508 proceeds to step 1610, where the FES offsetvalue is reset to 0 or, in some embodiments, is set to the best FESoffset value.

In step 1611, algorithm 508 increases by a set amount the FES offsetvalue in order to determine if a maximum TES peak-to-peak value can belocated in the increasing FES offset direction. Again, if the measuredTES peak-to-peak value is greater than the TES peak-to-peak value forthe current best FES offset value, then the best FES offset value is setto be the current FES offset value. In some embodiments of theinvention, algorithm 508 in step 1611 can increment beyond a maximum inthe measured TES peak-to-peak value by a number of increment steps wherethe TES peak-to-peak value decreases for each increment in the FESoffset value before exiting. Again, an error condition can be indicatedby exiting algorithm 508 through step 1607 and an abort condition can beindicated by exiting algorithm 508 through step 1609. Further, in someembodiments once a TES peak-to-peak value is located with the set amountof incrementation, a finer increment value can be utilized to moreaccurately find the TES peak-to-peak value. In some embodiments,algorithm 508 may search by incrementing the FES offset first and thendecrementing the FES offset second (e.g., reversing steps 1608 and 1611in FIG. 16A).

From step 1611 or step 1608, algorithm 508 proceeds to step 1612. Instep 1612, the FES offset value output from FES offset calibration canbe set to the best FES offset value. In step 1613, algorithm 508restores the TES gain and TES offset values that were saved in step1605. In step 1614, algorithm 508 restores tracking on (i.e., by closingtracking in tracking servo algorithm 502), provided that tracking was onin step 1602. Algorithm 508 exits at step 1615.

FIG. 16B shows another embodiment of FES offset calibration algorithm508. Again, FES offset calibration algorithm 508 begins at step 1601with a call to FESOffsetCal. In step 1650, algorithm 508 makes sure thatvoltages are brought to their operating levels (rather than remaining ina sleep mode). Step 1652 represents the top of a loop which ends atreturn step 1615. Step 1653 traps an abort request. The remainder of theembodiment of algorithm 508 shown in FIG. 16B is shown in state machineformat. In state 1671, the focus offset value is initialized to astarting value, for example 0×20. Algorithm 508 then proceeds to state1670. If optical media 102 is not spinning or focus is not closed, thenstate 1670 starts optical media 102 spinning and closes focus in focusservo algorithm 501, as shown in block 1602. Otherwise, state 1670transitions based on the parameter bCalStep. In the embodiment shown inFIG. 16B, algorithm 508 can transitions to a measure baseline state1655, a measure coarse negative state 1659, a current best offset upstate 1661, measure coarse positive state 1663, current best offset down1665, measure fine 1667, or final loop gain calibration state 1678. On afailure or error condition, algorithm 1670 can transition from state1670 or from any other state to command retry state 1672.

State 1672 can transition back to state 1670 to retry a particularcommand a set number of times. If the current command is notsuccessfully completed within that set number of times, then algorithm508 can transition from state 1672 to command cleanup state 1673. Instate 1673, algorithm 508 performs cleanup functions to recover from thefailure or from an abort command and transitions to final flags state1676. If an abort command is detected, then algorithm 508 transitionsthrough state 1674 to abort state 1675. From state 1675, algorithm 508transitions to command cleanup state 1673.

State 1670 can transition to final flags state 1676 when bCalSel is setto Final Flags Step. In state 1676, algorithm 508 sets the exit flags.If an error is detected, then algorithm 508 can transition through state1656 to command retry state 1672. Otherwise, algorithm 1676 transitionsto command complete state 1677 for exit at return 1615. State 1677 canset error flags if errors are detected and can set a flag indicatingsuccessful completion if algorithm 508 was successfully completed.

In step 1670, if bCalStep indicates a measure baseline function, thenalgorithm 508 transitions to measure baseline state 1655. State 1655measures the baseline value of the TES peak-to-peak curve by calculatingthe minimum and maximum value of the TES signal, as shown in block 1658.If state 1655 indicates an error, then algorithm 508 transitions throughstate 1656 to state 1672. If no error is indicated, the bCalStep is setto perform a coarse negative function and algorithm 508 transitionsthrough state 1657 back to state 1670.

If bCalStep is set to perform a coarse negative function, then algorithm508 transitions from state 1670 to state 1659. In state 1670, algorithm508 decrements the focus offset value to maximize the TES peak-to-peakvalue. If a maximum value is found by decrementing the focus offsetvalue, then the focus offset value is set to that value. In someembodiments, as shown in block 1660, a loop gain calibration of focusservo system 501 can be performed in state 1660. If state 1659 indicatesan error, then algorithm 508 transitions through state 1656 to state1672. Otherwise, bCalStep is set to current best offset up and algorithm508 transitions through state 1657 to state 1670.

In state 1670, algorithm 508 transitions to state 1661 if bCalStep isset to current best offset. In state 1661, algorithm 508. State 1659finds the best FES offset possible by decreasing the offset. State 1661smoothly goes to the best offset found in state 1659. If state 1661indicates an error, the algorithm 508 transitions through state 1656 tostate 1672. Otherwise, algorithm 1661 can set bCalStep to measure coarsepositive and algorithm 508 can transitions through step 1657 to state1670. In some embodiments, a loop gain calibration on focus servo loop501 can be performed in state 1661 as indicated in block 1662.

From state 1670, if bCalStep is set to measure coarse positive, thenalgorithm 508 transitions to state 1663. In state 1663 the best FESoffset can be found by increasing FES offset. If an error is detected instate 1663, then algorithm 508 transitions through state 1656 to state1672. Otherwise, bCalStep can be set to calculate the current bestoffset down and algorithm 508 can transitions through state 1657 tostate 1670. In some embodiments, a loop gain calibration can beperformed in state 1663 as indicated in block 1664.

If bCalStep is set to calculate the current best offset down, thenalgorithm 508 transitions to state 1665. In state 1665, algorithm 508smoothly goes to the best FES offset found in state 1663. If an error isdetected in state 1665, then algorithm 508 transitions through state1656 to state 1672. Otherwise, algorithm 508 can set bCalStep to measurefine bothways and transition through state 1657 to state 1670. In someembodiments, a loop gain calibration of focus servo loop 501 can also beperformed in state 1665.

If bCalStep is set to measure fine bothways, then algorithm 508transitions from state 1670 to state 1667. In state 1667, algorithm 508starts at the best FES offset and gain determined by states 1659 and1663 and take fine steps, in both positive and negative directions, tofind a point where the TES peak-to-peak becomes significantly reduced.If an error is detected in state 1667, then algorithm 508 transitionsthrough state 1656 to state 1672. Otherwise, bCalStep can be set to loopgain cal and algorithm 508 can transition through state 1657 back tostate 1670.

If bCalStep is set to loop gain cal, then algorithm 508 transitions fromstate 1670 to state 1678. In state 1678 a loop gain calibration isperformed on the focus servo system 501. bCalStep can then be set tofinal flags and algorithm 508 can transition back to state 1670.

FIG. 17 shows a focus offset calibration algorithm 508 that provides abest read/write focus offset value. Algorithm 508 of FIG. 17 is a focusoffset jitter calibration starting at step 1701. In step 1702, algorithm508 of FIG. 17 a seek operation is performed, for example by performingmulti-track seek algorithm 557, to position OPU 103 over a section ofoptical media 102 which contains readable data. When step 1702 iscomplete, both focus servo 501 and tracking servo 502 are closed.

In step 1705, algorithm 508 of FIG. 17 adjusts the Focus Offset value.In step 1706, algorithm 508 adjusts the total open loop gain of thefocus servo loop (i.e., with focus servo algorithm 501 and the plant) toprovide a unity response at a crossover frequency. The crossoverfrequency is the frequency where the open loop transfer function for thefocus servo loop (i.e., including focus servo algorithm 501 and theplant) is unity. In some embodiments, the crossover frequency is about1.5 kHz. In step 1708, data jitter is measured. Additionally, jitter canbe measured by monitoring the byte error rate in a read operation. Insome embodiments, jitter can be measured by comparing the phasemeasurement from slicer 422 (FIG. 4) with the sync mark detector ofblock 426 (FIG. 4), for example.

In step 1709, algorithm 508 checks to see if the data jitter has beenminimized. If not, then algorithm 508 returns to step 1705 to adjust FESoffset further. Otherwise, in step 1710 algorithm 508 sets FES offset tothe optimum value and exits in step 1711.

FIGS. 18 and 19 show an embodiment of TES Offset Calibration 542 whichmay be executed in steps 1306 and 1308 of calibration algorithm 1301 ofFIG. 13. Again, TES Offset calibration 542 may include either an offsetcalibration based on optimum servo operation, as is shown in FIG. 18, oran offset calibration based on optimum read/write operation, as is shownin FIG. 19. In some embodiments, offset calibration 542 may includeembodiments based both on best servo operation and best read/writeoperation and may provide a TES Offset value that is a compromisebetween the TES offset based on best servo operation, as is shown inFIG. 18, and the TES offset based on optimum read/write operation, as isshown in FIG. 19. The compromise tracking error signal offset, forexample, can be a weighted average between the TES offset that optimizesservo function and the TES offset that optimizes read function. Changingthe TES offset often means that OPU 103 is not tracking over trackcenters, but off the track center. Therefore, drive 100 may be lessstable. For example, a bump in one direction may more easily losetracking. Additionally, other parameters, for example tracking loopgain, may be incorrect for the particular TES offset.

In FIG. 18, TES offset algorithm 542 is initiated at step 1801 where itis called. In step 1802, algorithm 542 checks whether focus is closed infocus servo algorithm 501 and that spin motor 101 is spinning (see theSpin Motor Servo System disclosures). If an error is detected (forexample if focus is on but optical media 102 is not spinning), thenalgorithm 542 exits through step 1808 while setting an error flag. Errorrecovery routines are further described in the System Architecturedisclosures. If an abort condition is detected, then algorithm 542 exitsthrough step 1809 indicating an abort.

Algorithm 542 then proceeds to step 1803. In step 1803, if tracking ison algorithm (i.e., tracking servo system 502 is closed), 542 proceedsto step 1804 to shut tracking off. Once tracking is off, algorithm 542proceeds to step 1805. In step 1805, the current TES gain and thecurrent TES offset are saved. In step 1806, the TES offset value is set.In some embodiments, the TES offset can be set to zero. In otherembodiments, the TES offset may be left at the current TES offset valueor may be set at another default value. In some embodiments, algorithm542 may also reset the TES gain value at step 1806 to a default value.In some embodiments, the TES gain value is left at the current TES gainvalue. Algorithm 542 then proceeds to step 1807.

In step 1807, algorithm 542 checks to be sure that focus servo algorithm502 indicates a focus closed condition. If focus is lost, then algorithm542 can exit through step 1808 indicating an error message. Again, if anabort condition exists, then algorithm 542 can exit through step 1809.Algorithm 542 then proceeds to step 1810.

In step 1810, algorithm 542 determines the minimum and maximum values ofthe TES signal. Since tracking is off, the TES signal is a sinusoidalsignal that transitions a period of the sine wave as a track passesbeneath OPU 103. From averaging the minimum and maximum values, thecenter of the sinusoidal TES signal can be determined. This measured TESoffset signal can be stored as variable s_(—)1SignalOffset. In someembodiments, the average minimum and maximum values over a number ofperiods of the TES signal can be utilized to determine the measured TESoffset signal.

In step 1811, algorithm 542 checks whether the measured TES offset valueis zero. If it is, then in step 1812 a counter is set to iCalNum+1. Ifnot, then iCount is incremented and algorithm 542 proceeds to step 1813.In step 1813, an offset is set to the TES offset minus the measured TESoffset. In step 1814, the calculated offset is truncated. In step 1815,the TES offset is set to the offset value calculated in step 1814. Instep 1816, the counter iCount is checked to determine if it is less thaniCalNum+1. If so, then algorithm returns to step 1807. In step 1807, ifiCount is equal to iCalNum then a time-out error condition can be setand algorithm 542 can exit through step 1808.

If iCount is greater than iCalNum, indicating that an optimum TES offsetvalue has been found, then algorithm proceeds to step 1817 where theoptimum TES Offset value is stored. The TES gain value is also reset instep 1817. In step 1818, algorithm 542 closes tracking in tracking servoalgorithm 502 if tracking was on when algorithm 542 was called.Algorithm 542 can then exit normally through step 1819.

FIG. 19 shows a TES offset calibration algorithm 542 that sets the TESoffset based on optimum read/write conditions. Algorithm 542 as shown inFIG. 19 is called at step 1901. In step 1902, OPU 103 is position overreadable data on optical media 102. In some embodiments, OPU 103 ispositioned over the middle of the optical media 102. In someembodiments, OPU 103 is positioned over optical media 102 andmulti-track seek algorithm 557 is utilized to position OPU 103 overreadable data on optical disk 102. In step 1903 algorithm 542 closesfocus in focus servo algorithm 501 and in step 1904 algorithm 542 closestracking in tracking servo algorithm 502.

In step 1905, algorithm 542 adjusts the TES offset value. The TES offsetvalue may be incremented in either direction (i.e., increasing ordecreasing). If incrementing the TES offset value in the first directionis not successful, then algorithm 542 can increment the TES offset valuein a second direction. Further, the starting TES offset value may be theoptimum TES offset value calculated by algorithm 542 as shown in FIG.18.

In step 1906, the TES gain is set to provide a total open-loop gain ofunity at a TES crossover frequency. The TES crossover frequency is thefrequency that the open loop gain is set to unity. In some embodiments,the TES crossover frequency is about 1.8 kHz. In step 1907, data jitteris measured. Data jitter can be measured as described with step 1708 ofFIG. 17. In step 1908, algorithm 542 checks to see if the data jitterdetermined in step 1907 is at a minimum. If not (i.e., if the datajitter continues to decrease as TES offset is incremented), thenalgorithm 542 returns to step 1905.

An optimum TES offset value can be determined when data jitter had beendecreasing with additional TES offset increments but now is increasing.If an optimum TES offset value has been located, algorithm 542 proceedsto step 1909 where the TES offset value is stored. Algorithm 542 canthen exit at step 1910.

FIG. 20 shows an embodiment of TES gain calibration 544, which can beexecuted in step 1307 of calibration algorithm 1301 shown in FIG. 13.Algorithm 544 is called at step 2001 and proceeds to step 2002. Aninitial value of the TES gain can be passed to algorithm 544. Theinitial value can be the current value of the TES gain or a defaultvalue of the TES gain. In step 2002, algorithm 544 determines that focusis closed in focus servo algorithm 501 and that optical media 101 isspinning. If focus is not closed or optical media 101 is not spinning,algorithm 544 exits with an error flag set in step 2006. If an abortcondition is detected during step 2002, algorithm 544 exits with anabort flag set through step 2007. If step 2002 exits normally, algorithm544 proceeds to step 2003. In step 2003, if tracking is on, algorithm544 proceeds to step 2004 to turn tracking off and then proceeds to step2005, else algorithm 544 proceeds to step 2005. In some embodiments, OPU103 can be positioned over a particular zone or a particular media typeon optical medium 102 in step 2002.

In step 2005, algorithm 544 checks for a focus closed condition (a focusclosed condition can be indicated by the focus OK flag set by focus OKalgorithm 536). If focus has opened, then algorithm 544 can exit with anerror flag through step 2006. Again, if an abort condition is detected,algorithm 544 can exit with an abort flag set through step 2007. Iffocus is closed and no error or abort conditions are detected, thenalgorithm proceeds to step 2008.

In step 2008, algorithm 544 determines the minimum and maximum values ofthe TES sinusoidal signal. Step 2008 may include TES P-P algorithm 545.In particular, algorithm 544 determines the peak-to-peak values_(—)1PeakPeak of TES. In step 2009, a gain factor is calculated basedon the peak-to-peak value determined in step 2009 and a referencepeak-to-peak value TES_GAIN_REF. In some embodiments, the gain factor isa ratio between the reference peak-to-peak value and the measuredpeak-to-peak value of the TES signal. In step 2010, algorithm 544 checksto be sure that the gain factor is between a lower and upper limit, forexample between 0.25 and 4, to insure that the TES gain is not variedtoo quickly or too slowly. If the gain factor is outside of the range,then the gain factor can be reset to be the extreme value in the range.

In step 2011, a gain value is set to the TES gain times the gain factor.In step 2012, algorithm 544 checks to be sure that the gain value isbetween set limits (for example between −128 and +128). If the TES gain(the gain value) is outside of the set limits, then an error flag can beset. Otherwise, the TES gain is set to the gain value in step 2013 andalgorithm 544 proceeds to step 2014.

In step 2014, if counter iCount is less than a maximum and the gainfactor is not 1, then algorithm 544 returns to step 2005. In step 2005,iCount is incremented and an error condition may be set resulting inalgorithm 544 exiting through step 2006 if iCount is the maximum iCount.If the gain factor is one, then algorithm 544 has converged on a TESgain value and proceeds to step 2015. In step 2015, algorithm 544 turnstracking on if it was on when algorithm 544 started in step 2001 andexits normally at step 2016.

FIG. 21 shows a loop gain calibration algorithm 2100 which can be eitherfocus loop gain calibration 522 executed in step 1309 of calibration1301 of FIG. 13 or tracking loop gain calibration 562 executed in step1310 of calibration 1301 of FIG. 13. Both focus loop gain calibration522 and tracking loop gain calibration 562 operate in essentially thesame fashion. In focus loop gain calibration 522 a sine wave disturbanceat the desired cross-over frequency is generated in sine wave generator528 and applied through summer 523 to the focus control effort. Adiscrete Fourier transform from DFT 527 of the focus control effortbefore summer 523 is compared with a discrete Fourier transform from DFT525 of the disturbance in gain calculation 526 to determine the gain ofloop gain amplifier 524 so that the overall open loop gain at thecross-over frequency is 0 dB. Similarly, in tracking loop gaincalibration 562 a sinusoidal disturbance at a tracking cross-overfrequency (which, in general, can be different from the focus cross-overfrequency) is generated by a sine wave generator 568 and applied to thetracking control effort through summer 563. A discrete Fourier transformfrom DFT 567 of the tracking control effort before summer 523 iscompared with a digital Fourier transform from DFT 565 of thedisturbance is compared in gain calculation 566. The gain of loop gain564 can be set so that the tracking total open loop gain is 0 dB. Insome embodiments, the cross-over frequency for focus loop calibration522 can be about 1.5 kHz and the cross-over frequency for tracking loopgain calibration 562 can be about 1.8 kHz.

In FIG. 21, loop gain algorithm 2100 represents the generalized loopgain calibration algorithm which can be executed as focus loop gaincalibration 522 or tracking loop gain calibration 562. Algorithm 2100 isstarted at step 2101 when it is called. Algorithm 2100 then proceeds tostep 2102. In loop gain algorithm 2100, the loop that is currently beingcalibrated is closed. In some embodiments, focus loop gain calibration522 can be executed without closing tracking. However, for tracking loopgain calibration 562 both focus and tracking are closed.

In step 2102, algorithm 2100 executes a Bode algorithm at the crossoverfrequency. An embodiment of the Bode algorithm is further described inFIG. 22. In essence, the Bode algorithm executed in step 2102 disturbsthe loop at the frequency indicated (in step 2102 at the crossoverfrequency), performs a discrete Fourier transform (DFT) on both thedisturbance and the resulting measured signal, compares the twotransforms, and returns gain values for the indicated frequency withinthe range of frequencies. Therefore, in step 2102 the Bode algorithmreturns the total loop gain at the crossover frequency.

Once the loop gain at the crossover frequency is obtained in step 2102,it is inverted in step 2103 and multiplied by the current gain valuefrom block 2105 in step 2104 to form the new loop gain value. The newloop gain value is the gain value required so that the loop gain of theoutput signal from loop gain amplifier (amplifier 524 in focus loop gain522 or amplifier 564 in tracking loop gain 562) at the crossoverfrequency is, for example, 0 dB. In some embodiments, in order to obtaina larger dynamic range with a limited number of available bits, the gainof the loop gain amplifier is segregated into a gain and a shift term.The total gain being the gain*2^(shift). Therefore, in some embodimentsalgorithm 2100 spreads the new loop gain value into a gain and a shiftterm in step 2106. For example, in some embodiments data is sent in 16bit words and the loop gain value can be segregated into a 12 bit gainterm and a 4 bit shift term. A much larger dynamic range can be realizedwith only a slight loss in resolution. In step 2107, algorithm 2100saves the new gain of the loop gain amplifier. Algorithm 2100 exitsnormally in step 2108.

FIG. 22 shows an embodiment of a GetBode algorithm 2200 which can beexecuted in step 2102 of loop gain calibration algorithm 2100 of FIG.21. In general, a Bode algorithm determines the frequency response ofany pair of signals in a servo loop by disturbing the loop (for exampleat summer 523 or 563 in FIG. 1) with a known disturbance and measuringthe response of the loop to that disturbance. Bode algorithm 2200 startswhen called at step 2201. Several parameters can be passed to Bodealgorithm 2200, including a start frequency and an end frequency, aparameter indicating which loop to disturb (either tracking or focus),an oscillator amplitude value (which may be different for tracking servoloop or focus servo loop), the number of averages to compute, whether ornot notch filters in the loop will remain active during the calibration,whether or not tracking must stay closed during the calibration, whetherautogain is turned on or off, and whether to use floating or fixed pointmath. Step 2202 indicates an initialization step. Step 2203 indicatesthe top of a loop, which finishes when the calibration sequence ofalgorithm 2200 is completed.

The remainder of algorithm 2200 is shown in state diagram format. Fromstep 2204, algorithm 2200 enters introduction state 2217 where softwarepointers are initialized to point to the variables representing thetransfer functions numerator and denominator (e.g., TES, FES, andTracking Control E_(f)forts). Additionally, introduction state 2217turns off auto jump back if it is -enabled. From introduction state2217, algorithm 2200 enters a memory allocation state 2204. In memoryallocation state 2204, algorithm 2200 allocates sufficient memory toperform the Bode calculation of algorithm 2200. In some embodiments,allocation of memory can be done separately for each frequency becausethe trace length can be different for each frequency. A trace lengthinversely proportional to the frequency can yield better frequencyresolution.

If insufficient memory is available, algorithm 2200 transitions to freememory state 2214 where any memory which is already allocated is freed.From free memory state 2214, algorithm 2200 transition can transitionback to state 2214 if Bode calculations are to be done on furtherfrequencies or to calibration finished state 2215, which closes the loopstarted in step 2203, if the calculation is finished. If there is notsufficient memory available to perform the calculation, algorithm 2200can exit at step 2216, indicating an insufficient memory errorcondition.

If state 2204 allocates sufficient memory, then algorithm 2200transition to state 2205. In state 2205, algorithm 2200 tests to insurethat focus is closed and, if indicated, tracking is closed. If focus isopen, then state 2205 closes focus. If tracking is open and should beclosed, then state 2205 closes tracking. If there is not enough memory,algorithm 2206 can transition to free memory state 2215 to freeadditional memory.

Once the requested loops are closed in state 2205, algorithm 2200transitions to state 2206. In state 2206, an oscillator operating at aselected frequency is turned on. On the first pass through algorithm2200, the selected frequency is the start frequency. On subsequentpasses, the selected frequency is between the start frequency and theend frequency. The oscillator applies a sinusoidal disturbance to thefocus or the tracking loop, as indicated. The amplitude of thedisturbance depends on previous measurements. For example, if there is apositive slope in the response data the amplitude can be decreased andif there is a negative slope the amplitude can be increased. Algorithm2206 then transitions to either state 2207 if an auto-gain is set on orto collect samples 2208 if auto gain is set off. If auto-gain is on, thedisturbance amplitude is adjusted so that the maximum peak-to-peakvalues for TES and FES are sufficiently close to a target value. Ifeither TES or FES are too large, the disturbance amplitude is decreased.If both are too small the disturbance amplitude is increased. In someembodiments, TES and FES can be monitored directly for frequencies belowa threshold frequency, for example about 8 kHz, while the peak-to-peakvalues are monitored at frequencies above this frequency. Autogain state2207 can be looped with validate samples 2210 to ramp up the disturbanceamplitude. In validate samples state 2210, algorithm 2200 verifies thatfocus is still closed and, if required, tracking is still closed.Algorithm 2200 transitions through the loop including state 2207 and2210 until the amplitude of the disturbance generated in state 2206 isset. When complete, algorithm 2200 transitions to state 2208.

In state 2208, trace data is taken. Trace data includes data with thedisturbance and data measured from the control effort. As an example,state 2206 may turn sine wave generator 528 on and state 2208 thencollects trace data from the input signal to summer 523 and trace datafrom the output signal from summer 523, trace 1 and trace 2,respectively. Once trace data for both trace 1 and trace 2 is taken fora sufficient amount of time, algorithm 2200 transitions to state 2209.

In state 2209, the disturbance turned on in state 2206 is shut off andalgorithm 2200 transitions to state 2210. In state 2210, algorithm 2200verifies that focus is still closed and, if required, tracking is stillclosed. In some embodiments, algorithm 2200 can also check whether tracedata in trace 1 and trace 2 has a sufficient peak-to-peak amplitude. Iftrace data is not valid, for example because loops have opened, thenalgorithm 2200 transitions to state 2211. In state 2211, algorithm 2200attempts to repeat the measurement of the trace data. If focus ortracking loops have opened, then the amplitude of the sinusoidaldisturbance started in state 2206 can be decreased. Once algorithm 2200has adjusted parameters (e.g., the amplitude of the sinusoidaldisturbance), then algorithm 2200 transitions back to state 2205. If toomany retries have been attempted, then algorithm 2200 can transition tostate 2213 and set an error flag.

If algorithm 2200 finds valid data in state 2210, algorithm 2200transitions to state 2212. In state 2212, the amplitude of both trace 1and trace 2 data at the frequency of the sinusoidal disturbance iscalculated. Once the calculations are completed in state 2212, algorithm2200 transitions to state 2213. In state 2213, the ratio between theamplitude of trace 1 to the amplitude of trace 2 is calculated.Algorithm 2200 then transitions to state 2214. Algorithm 220 can freethe memory utilized in the previous calculation. If an error flag hasbeen set or if the Bode calculation is complete, then algorithmtransitions to state 2215 and then finishes at state 2216. Otherwise,algorithm 2200 increments the frequency and transitions to state 2204 toallocate memory for the calculation at the next frequency.

FIG. 23 shows an embodiment of a discrete Fourier transform algorithm2300 (DFT) that can be utilized with Get Bode algorithm 2200 of FIG. 22.DFT algorithm 2300 can be utilized anywhere, for example in DFTalgorithms 527, 525, 567, and 565. In some embodiments, fixed point mathcan be utilized to execute the calculations described. In someembodiments, floating point math can be executed. Although algorithmsexecuted with fixed point math can be much faster, algorithms executedwith floating point math are more accurate and less prone to overflowproblems.

Algorithm 2300 starts when called at step 2301. In step 2302, variablesR and I are initialized. In step 2303, further variables RealComp andInagcomp are set to zero and the trace pointer is set to 0. In step2304, algorithm 2300 checks to see if the sine and cosine coefficients(R and I) exist for the current point on the trace indicated by thetrace pointer. If not, then the sine and cosine coefficients R and I canbe computed in step 2305. Otherwise, algorithm 2300 proceeds to step2306. In step 2306, algorithm 2300 checks for a missed sample to assurethat it keeps the sine and cosine sample instants time aligned with themeasured waveforms time instants. If a sample is missed in themeasurement, then the algorithm must skip a sample in the sine andcosine coefficient before performing the product. If not, then algorithm2300 accumulates the product of the trace with the sine and cosinecoefficients in step 2307. Additionally, the trace pointer can beincremented in step 2307. In step 2308, the pointers to the sine andcosine coefficients are incremented. In step 2309, if there is moretrace data, algorithm 2300 returns to step 2304. If all of the tracedata has been processed, then algorithm 2300 proceeds to step 2310 wherethe amplitude of the accumulation computed in step 2307 is computed. Instep 2311, the amplitudes are accumulated. In step 2312, if there aremore averages to be processed, algorithm 2300 proceeds to step 2303.Otherwise, algorithm 2300 computes the average amplitude in step 2303and exits at step 2314.

FIG. 24 shows an embodiment of TES-to-FES Cross Talk Gain Calibrationalgorithm 579. As shown in FIGS. 5A and 5B, cross-talk gain calibration579 disturbs the tracking control effort by adding in a sinusoidaldisturbance from sinewave generator 581 to summer 563. Crosstalk Gaincalibration 579 then measures the FES output from cross-talk summer 513,calculates the single point DFT at the disturbance frequency, andadjusts a gain in ratio calculation 582, which normalizes the frequencycomponent in FES to the output of sine wave generator 581, in order tominimize the frequency component present in FES. The frequency of theperturbation induced by sine wave generator 581 is is chosen to providethe best overall calculation. In general, crosstalk is not a strongfunction of frequency. Therefore, whatever frequency that is convenient(i.e. stable) can yield good results. In some embodiments, one of thecross-over frequencies can be utilized, for example 1.5 kHz or 1.8 kHz.

FIG. 24 shows a block diagram of an algorithm for performing crosstalkcalibration 579. Before executing crosstalk calibration 579, focus andtracking are both on. Algorithm 579 is called in step 2401 with bothfocus and tracking on. In step 2402, algorithm 579 initializesvariables. In step 2403, algorithm 579 starts a loop that finishes whenalgorithm 579 determines that calibration of the crosstalk gainparameter to cross-coupling gain 514 is determined.

The remainder of algorithm 579 is shown in state function format. Instate 2404, algorithm 579 allocates sufficient memory to perform thealgorithm. If sufficient memory is not available, algorithm 579transitions to step 2409 which frees any memory that has been allocated.Algorithm 579 then transitions to step 2410 where the loop started instep 2403 is terminated. Finally, algorithm 579 exits with an error flagset at step 2411.

If there is sufficient memory so that algorithm 579 allocates memory instate 2404, then algorithm transitions to state 2405. In state 2405,algorithm 579 sets an initial crosstalk gain that can be utilized incross-coupling gain 514 (FIG. 5A). Algorithm 579 can set the initialcrosstalk gain by reading default values from a default file or byreading the last crosstalk gain value from program memory 330 or byreading the last crosstalk gain value utilized with optical media 102from optical media 102. Further, the best cross-talk gain value is setto the initial cross-talk gain variable. Once the initial value of thecrosstalk gain parameter is set, algorithm 579 transitions to state2406.

In state 2406, algorithm 579 performs a Bode calculation by, forexample, calling GetBode algorithm 2200 of FIG. 22. GetBode algorithm2200 inputs a disturbance into the tracking loop at the desiredfrequency, for example at the tracking crossover frequency (e.g., 1.8kHz). GetBode algorithm 2200, as executed in state 2406, measures theFES output from summer 513, and calculates the amplitude of the FES atthe disturbance frequency. The returned value from the Bode Calculationperformed within state 2406, then, is the signal component amplitude atthe frequency of the disturbance. If the amplitude is lower at thiscrosstalk gain than the lowest so far, then the best crosstalk gainvariable is set to the gain value. If the crosstalk does not have asmaller amplitude at the present crosstalk gain value, then algorithm579 transitions to state 2407.

In state 2407, algorithm 579 increments or decrements the cross-talkgain and returns to state 2406. In some embodiments, algorithm 579 maystart at an initial gain and increment through a range of gains in orderto determine the best cross-talk gain. In some embodiments, algorithm579 can start at an initial gain and move the gain in a first direction.If the cross-talk is increased by a move in the first direction, thenalgorithm 579 can move the cross-talk gain in the opposite directionfrom the first direction until a cross-talk gain that provides a minimumamount of TES-FES cross-talk is found. In some embodiments, algorithm579 can search well beyond a located minimum (for example about 5increments) to insure that the located minimum is actually a minimum.

In state 2406, when algorithm 579 discovers that it has checked eachgain value or if a gain value that results in a minimum amount ofcross-talk has been found, state 2406 transitions to state 2408. Instate 2408, algorithm 579 stores the new cross-talk gain value andtransitions to state 2409. In state 2409, algorithm 579 frees the memoryallocated in state 2404 and transitions to state 2410. In state 2410,algorithm 579 ends the search loop and exits normally at step 2411.

FIG. 25 shows an embodiment of a notch filter calibration algorithm2500. Algorithm 2500, for example, can be notch filter calibration 552in tracking servo algorithm 502 or notch filter calibration 520 in focusservo tracking algorithm 501. Notch calibration algorithm 2500 is calledin step 2501. In step 2502, algorithm 2500 performs a Bode calculationby, for example, calling Get Bode algorithm 2200 of FIG. 22 in order toobtain the frequency response curve of the appropriate control loopwithin a particular frequency range. The frequency response curveindicates the amplitude of the discreet Fourier transform at selectedfrequencies within the frequency range. In some embodiments, Get Bodealgorithm 2200 of FIG. 22 provides ratios of single point DFTs atdiscrete frequencies in the frequency range. For example, notchcalibration 520 can calibrate notch filter 519 in the range of about 3to about 5 kHz. Get Bode algorithm 2200 returns an array providing theamplitude of the frequency response for, for example, the focus servoloop or the tracking servo loop. In step 2503, algorithm 2500 locatesmaximum peaks in order to determine the frequencies at which maximumresponses are obtained. In some embodiments of the invention, peaks overa threshold value are targeted so that frequencies corresponding toresponses above a certain amount are found. In some embodiments, acertain number of peaks are found, regardless of the magnitude of theactual response. The frequencies at which maximum responses are obtainedare passed out of routine 2500, for example to a notch filter whichfilters the control signal at those frequencies. Algorithm 2500 thenexits at step 2504.

If notch calibration algorithm 2500 is being executed as notchcalibration 520, then the Bode algorithm 2500 disturbs the focus controleffort and reads the responsive FES signal at the output of phase lead518. The frequencies at which maximum responses are measured are passedto notch filter 519 so that a notch filter can be established aroundthose frequencies. If notch calibration algorithm 2500 is being executedas notch calibration 552, then the Bode algorithm 2500 disturbs thetracking control effort and reads the responsive TES signal at theoutput of phase lead 550. The frequencies at which maximum responses aremeasured are passed to notch filter 551.

In some embodiments, focus is closed before algorithm 2500 is called asnotch calibration 520. In some embodiments, focus and tracking areclosed before algorithm 2500 is called as notch calibration 552.

FIG. 26 shows an embodiment of a feed-forward algorithm 2600.Feed-forward algorithm 2600 can be utilized as feed-forward block 532 infocus servo algorithm 501 and feed-forward block 579 in tracking servoalgorithm 502. Feed-forward algorithm 532 monitors the focus controleffort output from multiplexer 531 for harmonic variations which, forexample, can be the result of warping of optical media 102, bearing wearof spin motor 101, or other factors which can cause a periodic variationin the FES signal. Similarly, feed-forward algorithm 579 monitors thetracking control effort for periodic variations. Once detected, theperiodic variation in the FES signal can be anticipated by feed-forwardalgorithm 532 and OPU 103 can be moved with the same periodicity and anappropriate amplitude so that the periodic variation is effectivelyremoved from FES. Similarly, periodic variations in TES can beanticipated by feed-forward algorithm 579 and control arm 104 can bemoved periodically to remove these variations from TES.

Therefore, when operating fully and settled, feed-forward algorithm 532and feed-forward algorithm 579 monitors the focus control effort and thetracking control effort and provide periodic control efforts that resultin the removal of the effects of the anticipated motion from the FES andTES signals, respectively.

In some embodiments, algorithm 2600 removes periodic variations whichare harmonics of the spin frequency of optical media 102 (i.e., of therotation frequency of spin motor 101). Therefore, the output signal fromalgorithm 2600, the period variations, can be expressed as A sin ωt+Bcos ωt, where ω is the rotation frequency of spin motor 101. The outputsignal from feed-forward algorithm 532, then, is input to summer 533 andthe output signal from feed-forward algorithm 579 is input to summer578.

Turning to algorithm 2600 of FIG. 26, a square-wave clock signal isprovided which has a frequency equal to the frequency of spin motor 101times the length of a sine-wave look-up table utilized to generate thesine wave. A delay parameter is also passed to algorithm 2600 whichdetermines the number of clock cycles to delay before re-sampling theinput signal and updating the parameters of the output signal fromsummer 2616. Further, the number of cycles to sample is input toalgorithm 2600.

The input signal is received by multipliers 2602 and 2603. In general,the input signal is of the formf(t)=a sin ωt+b cos ωt+g(t),where a and b are the coefficients of periodic control effort yet to beremoved from the control effort and g(t) is the control effort whichdoes not include a component of the spin-motor frequency. Upon startup,the entire amount of the periodic correction can be included in theinput signal f(t) and therefore a=A and b=B. During operation, smallcorrections on the output parameters A and B are included in the inputsignal f(t).

The input signal f(t) is multiplied by sin(ωt) in multiplier 2602 andmultiplied by cos(ωt) in multiplier 2603. The output signal frommultiplier 2602, f(t)sin ωt, is input to multiplexer 2609 and the outputsignal from multiplier 2603, f(t)cos ωt, is input to multiplexer 2608.

Countdown timer 2605, can be loaded with the delay parameter and, oneach clock cycle, counts down. During the delay period, countdown timer2605 outputs a select signal that selects the grounded input tomultiplexers 2609 and 2608. Once countdown timer 2605 reaches zero(indicating the end of the delay period), then timer 2605 outputs aselect signal to multiplexers 2609 and 2608 which selects the outputsignals from multipliers 2602 and 2603, respectively.

The output signals from multiplexer 2609 and 2608 are input to summers2610 and 2611, respectively. Summer 2610 sums its input with its output.Summer 2610 starts each sampling period with a zero'd output signal.Between the end of the delay period and the end of the sample period setby the signal DFTCYCLES, summer 2610 sums the signal f(t)sin ωt overDFTCycles of periods of the sine wave. Therefore, at the end of thatsummation, the output signal from summer 2610 is related to thecoefficient a, all other products in f(t) being zero'd due to thesummation. Similarly, summer 2611 sums f(t)cos ωt over DFTCYCLES numberof periods so that the output signal from summer 2611 is related to thecoefficient b.

The number of cycles DFTCYCLES times the length of the sinetable iscalculated in multiplier 2606 and summed with the delay in summer 2607.Countdown timer 2617, then, counts down over the delay and the period inwhich summers 2610 and 2611 are accumulating. At the end of thecountdown period, countdown timer 2617 enables summers 2612 and 2613before starting the next period. During the period when summers 2612 and2613 are enabled, the output signal from summers 2610 and 2611,respectively, are added into the values already present. Summers 2612and 2613, then, hold the output values until, once again. summers 2610and 2611 are finished accumulating. The output signals from 2612 and2613 are multiplied by the sine function and the cosine function,respectively, and added in summer 2616 to provide an output signal ofthe form A sin ωt+B cos ωt, which is added to the control effort. Thecoefficients A and B are updated on each accumulation period. Eachaccumulation period, essentially, takes a single point DFT of the inputsignal to determine the ω frequency component of the input signal andoutputs that component.

In some embodiments of the invention, the calibrated parameters aredifferent for different track locations on optical media 102. Forexample, the OPU gain and offset values may be different betweenwriteable and premastered portions of optical media 102. In someembodiments, optical media 102 may be zoned with a number of zones. Insome embodiments, zones of the number of zones can include both writableand premastered portions. As such, parameters can be calibrated foroperation of different media types as well as different zones. FIGS. 27Aand 27B show an embodiment of an algorithm 2700 for calibratingparameters in different regions of optical media 102.

Algorithm 2700 is called at step 2701. In step 2702, a command stateparameter is set to calibration initialization. The top of thecalibration loop is started in step 2703. After step 2703, until thecalibration loop is completed, the algorithm is described by a statediagram. From step 2703, algorithm 2700 enters state 2704. In state2704, calibration parameters are initialized. Additionally, a currentzone parameter is set to the first zone to be calibrated.

Algorithm 2700 then transitions to state 2705. In state 2705, algorithm2700 checks whether all zones have been calibrated. If all of the zoneshave been calibrated, then algorithm 2700 transitions from state 2705 tostate 2713. In state 2713, the calibrated parameters are stored. In someembodiments, some or all of the parameters are stored in program memory330. In some embodiments, some or all of the parameters can be stored onoptical media 102.

If algorithm 2700 determines that all of the zones are not calibrated,then in state 2705, algorithm 2700 performs a seek operation to positionactuator arm 104 at a particular zone of optical media 102. Statealgorithm 2705 determines a desired track position for the current zoneand, in step 2706, calls seek algorithm 557 to position OPU 103 into thedesired zone of optical media 102. In some embodiments, before seekalgorithm 557 is called, algorithm 2700 may turn focus and tracking on,if focus and tracking are currently off.

If the seek algorithm initiated by algorithm 2706 fails then algorithm2700 transitions from state 2705 to state 2710. In state 2710, a cleanupalgorithm is executed. The cleanup algorithm may, for example, positionOPU 103 at a parking position and may open focus and tracking. Fromstate 2710, algorithm 2700 exits with an error flag set.

If, while in state 2705, algorithm 2700 detects an abort command, thenalgorithm 2700 transitions to state 2712. In state 2712, algorithm 2700acknowledges the abort command and transitions to state 2710 to executethe cleanup algorithm.

If, in state 2705, the seek was successful, then algorithm 2700transitions to state 2707. In state 2707, algorithm 2700 performs thecalibrations, for example by calling a zone calibration algorithm 2711.Zone calibration algorithm 2711 executes individual calibration routinesin order to calibrate the parameters within the current zone. In state2707, if an abort condition is detected, then algorithm 2700 transitionsto state 2712. If an error condition is detected (for example, if one ofthe calibration routines returns an error condition), then algorithm2700 transitions to state 2709.

In state 2709, algorithm 2700 increments a retry counter. If the retrycounter is above a certain value, then algorithm 2700 transitions tostate 2710 to exit. If the retry counter is still at acceptable levels,then algorithm 2700 transitions to state 2705 to attempt another try atcalibrating the current zone. In some embodiments, algorithm 2700 maytry to calibrate a particular zone several (e.g., about 3) times beforeexecuting a failed exit in state 2710.

In state 2707, if the calibration algorithms are executed without error,the algorithm 2700 transitions to state 2708. In state 2708, the resultsof the calibration are stored in one or more arrays 2715. Further, thecurrent zone is incremented to point at the next zone and algorithm 2700transitions to state 2705 to perform calibrations in the new currentzone.

FIG. 27B shows an embodiment of zone calibration algorithm 2711 which iscalled from state 2707 of algorithm 2700. Algorithm 2711 is called atstep 2730. In step 2731, a command initialize flag is set. In step 2732,drive 100 is brought to full power if drive 100 had previously beenasleep (or in lower power mode). In step 2733, the top of a calibrationloop is started. In step 2734, and throughout algorithm 2711, if anabort condition is detected then algorithm 2711 transitions to state2751 where the abort condition is acknowledged. Algorithm 2700 thentransitions to state 2750 where any cleanup routines (for example,parking OPU 103 or turning focus and tracking off) are executed. Fromstate 2750, algorithm 2700 transitions to state 2754 where error andabort flags are set. Algorithm 2700 then transitions to state 2753 wherealgorithm 2700 exits the loop started with step 2733. Finally, algorithm2711 exits at step 2756 with any abort or error flags set.

From step 2734, with no abort condition detected, algorithm 2711transitions to state 2735. In state 2735, tracking and focus are bothturned off, if they are on, in step 2736. Further, operating parameters(e.g., OPU Offsets, OPU Gains, FES Offsets, FES Gains, FES Loop Gain,Notch filter parameters, TES offsets, TES gains, TES loop gains, TES-FEScross-talk gain) for the current zone are loaded. If an error conditionis detected in state 2735, then algorithm 2711 transitions to state2737. In state 2737, if only an acceptable number of retries have beenattempted, then algorithm 2711 transitions back to state 2735 to retryinitializing operating parameters and turning tracking and focus off. Ifan unacceptable number of retries have been attempted, algorithm 2711transitions to state 2750 to eventually exit at step 2756 with errorflags set. If no errors are detected in state 2735, then algorithm 2711transitions to state 2739.

In state 2739, algorithm 2711 starts spin motor 101. As discussed in theSpin Motor disclosures, state 2739 can call algorithms to stop themotor, start the motor, and set the spin speed in block 2738. If anabort flag is detected, algorithm 2711 can transition to state 2751. Ifan error is detected, then algorithm 2711 transitions to state 2740. Instate 2740, a retry is started. If too many retries have been attempted,then algorithm 2711 transitions to state 2750 to eventually exit at step2756 with error flags set. If not too many retries have been attempted,then algorithm 2711 transitions back to state 2739 to attempt to startspin motor 101 again.

If motor 101 is successfully started in state 2739, algorithm 2711transitions to state 2741. In state 2741, algorithm 2711 turns laser 218on and executes focus gain calibration 510. An embodiment of focus gaincalibration 510 is shown in FIGS. 15A and 15B, which have beenpreviously discussed. If an error is detected, then algorithm 2711transitions to state 2740 which, if not too many retries have beenattempted, transitions to state 2739 to retry states 2739 and 2741.Again, if too many retries are attempted, algorithm 2711 transitionsfrom state 2740 to state 2750. If an abort condition is detected instate 2741, then algorithm 2711 transitions to state 2751.

If algorithm 2711 in state 2741 successfully turns laser 218 on andexecutes a focus gain calibration in step 2742, then algorithm 2711transitions to state 2743. In state 2743, algorithm 2711 turns focus on.In steps 2744, state 2473 can start and stop motor 101, can set themotor speed of motor 101 to be appropriate for the current zone beingcalibrated, and can turn focus on by calling algorithm 535. Anembodiment of algorithm 535 is shown in FIG. 7A.

If an error is detected in state 2743, then algorithm 2711 transitionsto state 2747 to attempt a retry. If not too many retries have beenattempted, algorithm 2711 transitions back to state 2743 to againattempt to close focus. If too many retries have been attempted, thenalgorithm 2711 transitions to algorithm 2750 to shut laser 218 off, stopmotor 101 and park OPU 103 before setting error flags in state 2754 andexiting with error flags set in step 2756. If an abort condition isdetected, algorithm 2711 transitions to state 2751.

If state 2743 successfully closes focus, then algorithm 2711 transitionsto state 2745. In state 2745, calibration algorithms that operate withfocus closed can be executed. These algorithms, in step 2746, includefocus loop gain calibration 522 (an embodiment of which is shown in FIG.21), FES offset calibration 508 (embodiments of which are shown in FIGS.16 and 17), TES Offset calibration 542 (embodiments of which are shownin FIGS. 18 and 19), and TES Gain Calibration 544 (an embodiment ofwhich is shown in FIG. 20).

If an error is detected in state 2745, then algorithm 2711 transitionsto state 2747 to retry the calibrations. If too many retries have beenattempted, then algorithm 2711 transitions to state 2750 to turntracking and focus off, turn laser 218 off, and shut motor 101 downbefore exiting at step 2756 with error flags set. If not too manyretries have been attempted, then algorithm 2711 transitions back tostate 2743 to attempt to close focus and execute the calibrationalgorithms of step 2746 again.

If state 2745 executes the calibrations of step 2746 successfully, thenalgorithm 2711 transitions to state 2748. In state 2748, algorithm 2711closes focus and tracking. Furthermore, tracking is closed at aparticular track identified by a target PSA value. The target PSA trackis within the current zone. State 2748 may, in step 2749, executealgorithms to start and stop motor 101, execute focus close algorithm535, execute close tracking algorithm 555, and execute seek algorithm557 and one-track jump algorithm 559 in order to position OPU 103 at thetarget PSA (position address).

If state 2748 detects an error, then algorithm 2711 transitions to state2752. In state 2752, algorithm 2711 checks to see if the allowablenumber of retries has been exhausted. If not, then algorithm 2711transitions back to state 2748 to attempt to close focus and tracking onthe track identified by the target PSA once again. If the number ofretries has been exhausted, the algorithm 2711 transitions to state 2750to shut laser 218 off, open tracking and focus, shut motor 101 off, andeventually exit at step 2756 with error flags set. If an abort conditionis detected, algorithm 2711 transitions to state 2751.

If state 2748 successfully closes focus and tracking at the target PSA,then algorithm 2711 transitions to state 2755. In state 2755 calibrationalgorithms with both focus and tracking closed can be executed. Thesealgorithms, examples of which are shown in step 2757, includes trackingloop gain calibration 562 (an embodiment of which is shown in FIG. 21),focus loop gain calibration 522 (an embodiment of which is shown in FIG.21), and TES-FES crosstalk calibration 579 (an embodiment of which isshown in FIG. 24).

If an error is detected in state 2755, then algorithm 2711 transitionsto state 2752 to attempt a retry as discussed above. If no error isdetected, then algorithm 2711 transitions to state 2754. In state 2754,no error flags are set and algorithm 2711 prepares for a normal exit. Instate 2753, algorithm 2711 signals that the loop started in step 2733 iscompleted and algorithm 2711 exits in step 2756.

As shown in FIG. 27A, algorithm 2711 is executed through each definedzone on optical media 102. Therefore, a set of calibrated operatingparameters is stored with operating parameters which are appropriate foreach zone of optical media 102.

FIG. 28 shows an embodiment of inverse non-linearity calibration 512 infocus servo algorithm 501 and inverse non-linearity calibration 547 intracking servo algorithm 502. Non-linearity calibrations 512 and 514sets a gain versus offset (either TES offset or FES offset) table whichlinearizes the TES or FES signals around the offset values.Non-linearity calibrations 512 and 514 can be calibrated duringalgorithm 1301 of FIG. 13. Further, non-linearity calibrations 512 and514, in some embodiments, may be executed during zone calibrationalgorithm 2700 of FIG. 27. FIG. 28 shows an embodiment of algorithm 2800which builds a table of FES gain, TES gain, TES offset, tracking loopgain and TES-FES cross-talk as a function of FES offset. In general,algorithm 2800 may provide a table of FES gain versus FES offset, TESgain versus TES offset, or other combinations of parameters that resultin linear operation of a digital servo system.

In FIG. 28, algorithm 2800 starts when called at step 2801. In step2802, algorithm 2800 sets a CMD_INIT flag. In step 2803, algorithm 2800turns power on so that drive 100 is fully functional (rather thanasleep). Step 2804 starts the top of a loop. If an abort condition isdetermined, then algorithm 2800 transitions to state 2822 where theabort command is acknowledged. Algorithm 2800 then transitions to state2823 which shuts drive 100 down, for example, by opening tracking andopening focus, shutting laser 218 off, and shutting motor 101 off.Algorithm 2823 then transitions to state 2820 where abort flags can beset. Algorithm 2800 then transitions to 2821 to signal that the loopstarted with step 2804 is complete before exiting at step 2825 with anabort flag set.

If no abort condition is detected in step 2805, then algorithm 2800transitions to state 2806. In state 2806, operating parameters for drive100 as well as the non-linearity look up table initial parameters areloaded. Further, an initial offset is set in state 2806.

If an error is detected in state 2806, for example a mailboxcommunications error, then algorithm 2800 transitions to state 2823.Algorithm 2800 shuts drive 100 off (i.e., tracking off, focus off, laser218 off, motor 101 off) and transitions to state 2820. In state 2820,error flags are set. As shown in block 2824, normal calibration valuescan be restored from memory 320 or 330 (FIG. 3). Algorithm 2800 thentransitions to state 2821 which ends the loop started in step 2804.Algorithm 2800 then exits at step 2825.

If no errors are detected in state 2806, then algorithm 2800 transitionsto state 2807. In state 2806, algorithm 2800 initiates a set of OPUoffset values, indicated by arrays 2826. These values are specificoffsets used throughout algorithm 2800. In state 2807, algorithm 2800sets the FES offset. Algorithm 2800 then calibrates the FES gain inalgorithm 510. Further, algorithm 2800 sets a doing FES flag to TRUE anda doing TES flag to FALSE in state 2807. Algorithm 2800 then transitionsto state 2808.

In state 2808, algorithm 2800, in step 2809, insures that tracking andfocus are on. If an error is detected in state 2808, the algorithm 2800transitions to recovery state 2818. If too many recoveries have beenattempted in recovery state 2818, then algorithm 2800 transitions tostate 2823 and eventually exits with an error flag set in step 2825. Ifno error is detected in state 2808, then algorithm continues to state2809.

If the doing FES flag is TRUE, then algorithm 2800 transitions to state2809. In state 2809, algorithm 2800 measures the focus loop gain at across-over frequency. The cross-over frequency can be, for example, 1.5kHz. Algorithm 2800 may, for example, call GetBode algorithm 2200 inFIG. 22 in step 2810. If the loop gain at the cross-over frequency isclose to unity, then algorithm 2800 sets the doing TES flag to TRUE andtransitions back to state 2808. If the loop gain is not yet unity, thenalgorithm 2800 transitions to state 2811.

In state 2811, the FES gain is adjusted. In some embodiments, the FESgain is adjusted in a first direction and if the loop gain is determinedto be farther from unity than with the last adjusted FES gain, then theFES gain is adjusted in the opposite direction. Once the FES gain isadjusted in state 2811, then algorithm 2800 transitions to state 2809 tore-measure the loop gain with a new FES gain. Again, if an error isdetected in state 2809, then algorithm 2800 transitions to state 2818 toattempt a retry.

From state 2808 if doing TES is TRUE, then algorithm 2800 transitions tostate 2812. In state 2812, algorithm 2800 executes the TES gaincalibration algorithm 544 and the TES offset calibration 542. If anerror is detected in state 2812, then algorithm 2800 transitions tostate 2818 to attempt a retry. If no error is detected in state 2812,then algorithm 2800 transitions to state 2813

In state 2813, algorithm 2800 executes tracking loop gain calibration562 in step 2815. If an error is detected in state 2813, then algorithm2800 transitions to state 2818. If no error is detected, then algorithm2800 sets the doing FES flag to FALSE and the doing TES flag to FALSEand transitions to state 2816.

In state 2816, algorithm 2800 executes TES-FES crosstalk gaincalibration 579. In some embodiments, as shown in block 2817, algorithm2800 can move OPU 103 to a particular position on optical medium 102,for example the outer rim. Algorithm 2800 then transitions to state2819. In state 2819, the results of the linearity calibration for theselected FES offset is stored in arrays 2826. Algorithm 2800 may, forexample, store the results in flash memory 330. If algorithm 2800determines that algorithm 2800 is not finished (i.e., values for eachFES offset have not been determined), then algorithm 2800 transitionsback to state 2807 to pick the next FES offset value. If algorithm 2800determines that all of the FES offset values have been considered, thenalgorithm 2800 transitions to state 2820.

In state 2820, drive 100 is shut off and normal exit flags are set.Algorithm 2800 then transitions to state 2821, which ends the loopstarted with step 2804. Algorithm 2800 then exits normally at step 2825.

From algorithm 2800, a table of FES gain, TES gain, TES offset, trackingloop gain, and TES-FES crosstalk gain is tabulated for each value of FESoffset. These parameters are then set during operation in inversenon-linearity algorithms 511 and 546. In some embodiments, the FES andTES calculations are very sensitive to the current focus position (theFES offset value). Algorithms 512 and 547 build a table of gains whichaccount for the nonlinear effects in FES and TES. Blocks 511 and 546,then, can use these tables of gains to change the FES and TES gains inorder to keep the response linear.

FIG. 29 shows an embodiment of a head load algorithm 2900. When drive100 is started, the position of the OPU over optical media 102 isunknown. Head load algorithm 2900 allows drive 100 to be started andfocus and tracking to be closed over a valid portion (i.e., a portionwith tracks) of optical media 102. The tracking control signal (biassignal) required to position OPU 103 in an open loop mode over thetracks of optical media 102 can be quite variable due to mechanical andelectronic parameter variation and the physical orientation of drive100. Head load algorithm 2900 starts at step 2901, where optical media102 is spun up by starting spindle driver 101. In step 2902, OPU 103 isbiased against the inner stop. In other words, the tracking controleffort is set at a value that insures that OPU 103 is positioned againstthe inner stop. Algorithm 2900 then moves to step 2903. In step 2903,algorithm 2900 closes focus, for example with focus close algorithm 535.In step 2904, the bias signal is incremented to move OPU 103 slightlyaway from the inner stop. In step 2905, the TES peak to peak value iscalculated. In some embodiments, in step 2902 OPU 103 is positioned atany extreme position (e.g., at the inner diameter of optical media 102or the outer diameter of optical media 102).

In some embodiments, optical media 102 has an inner portion 153 (FIG.1B) that includes a bar code pattern over about ½ of the circumference.The TES amplitude, while over the bar code pattern, is similar to theTES amplitude when over premastered portion 150, but the TES waveform isdifferent. FIGS. 30A and 30B show examples of the TES amplitude with OPU103 over the bar code area (BCA) of optical media 102. For comparison,FIG. 30C shows an example of the TES during a close tracking algorithm.In step 2905, algorithm 2900 collects TES signal data for approximatelyone revolution of optical media 102. In step 2906, algorithm 2900calculates the mean of the TES signal data collected in step 2905.

In step 2907, algorithm 2900 calculates a limit range based on the meancalculated in step 2905 and compares each sampled data in the TES datataken in step 2905 with that limit range. Algorithm 2900 counts thenumber of samples that are within the limits.

In step 2908, algorithm 2900 compares the count from step 2907 to athreshold limit. If the count is over the threshold limit, then OPU 103is over a readable portion of optical media 102 (i.e., a portion withtracks) and algorithm 2900 proceeds to step 2909. Otherwise, algorithm2900 returns to step 2904 to move OPU 103 out another increment.

Algorithm 2900 continuous to move OPU 103 away from the inner diameterof optical media 102 until algorithm 2900 determines that OPU 103 isover a portion of optical media 102 with tracks. In step 2910, algorithm2900 closes tracking. In some embodiments, track crossing detector 454can be utilized to determine if OPU 103 is moving to fast. In someembodiments, a fixed time delay after incrementing the bias signal toactuator arm 104 can be utilized.

When a newly inserted optical media 102 is inserted and drive 100 isstarted, the tracks under OPU 103 are of an unknown type (e.g., theycould be in a writeable portion or a premastered portion of opticalmedia 102). As discussed above, there are many operating parameters thatare media dependent (e.g., TES gain and offset, FES gain and offset).The media type can be determined by starting with parameters appropriatefor a premastered portion of optical media 102 and monitoring the TESpeak-to-peak signal with focus closed. The TES peak-to-peak signal ismuch larger (for example by about twice) for writeable tracks than forpremastered tracks. In some embodiments, algorithm 2900 includes step2909 executed before tracking is closed in step 2910. In step 2903,operating parameters appropriate for writeable portions of optical disk102 are loaded. In step 2909, if the TES peak-to-peak signal is below athreshold value then algorithm 2900 loads operating parametersappropriate to a premastered portion instead.

In some embodiments, the threshold value can be set to be between 50%and 100% of an expected peak-to-peak value for the TES over writeablemedia. If the threshold value is set too high or too low, however, thereis a greater likelihood of media miss-identification, resulting inloading of incorrect operating parameters.

CD ROM Appendix A is a computer program listing appendix that includessource codes for an embodiment of the present invention. A directory ofCD ROM Appendix A is given in Appendix B. Both CD ROM Appendix A andAppendix B are herein incorporated by reference in this application intheir entirety.

The above detailed description describes embodiments of the inventionthat are intended to be exemplary. One skilled in the art will recognizevariations that are within the scope and spirit of this disclosure. Assuch, the invention is limited only by the following claims.

APPENDIX A

See attached CD-ROM Copy 1 or Copy 2

APPENDIX B (Directory of CD ROM Appendix A) DATE CREATED TIME BYTESFILENAME Aug. 09, 2001 05:50p 17,301 Defin_h.txt Aug. 10, 2001 02:13p85,660 dservo_c.txt Aug. 09, 2001 05:47p 33,958 dspmem_h.txt Aug. 09,2001 05:45p 292,400 dspp_c.txt Aug. 09, 2001 05:44p 292,400 dsp_p_c.txtAug. 09, 2001 05:47p 4,287 engpar_h.txt Aug. 09, 2001 05:43p 7,688Focu_h.txt Aug. 09, 2001 05:48p 3,764 indus_h.txt Aug. 09, 2001 05:49p69,191 rpmtbl_h.txt Aug. 09, 2001 05:47p 96,378 scmd_c.txt Aug. 09, 200105:49p 7,414 SineTb_h.txt Aug. 09, 2001 05:46p 8,819 sintrp_c.txt Aug.09, 2001 05:45p 327,430 smain_c.txt Aug. 09, 2001 05:50p 27,961smain_h.txt Aug. 09, 2001 05:48p 97,596 sspin_c.txt Aug. 09, 2001 05:46p189,471 stint_c.txt Aug. 09, 2001 05:45p 57,381 stools_c.txt Aug. 09,2001 05:51p 2,185 stools_h.txt Aug. 09, 2001 05:51p 302,470 sutil_c.txtAug. 09, 2001 05:51p 30,265 sxtrn_h.txt Aug. 09, 2001 05:51p 11,063TrackC_h.txt Aug. 09, 2001 05:45p 25,479 XYram_h.txt

Directory of CD ROM Appendix Directory of D:\ 08/10/01 02:27p <DIR>08/10/01 02:27p <DIR> 08/09/01 05:50p 17,301 Defin_h.txt 08/10/01 02:13p85,660 dservo_c.txt 08/09/01 05:47p 33,958 dspmem_h.txt 08/09/01 05:45p292,400 dspp_c.txt 08/09/01 05:44p 292,400 dsp_p_c.txt 08/09/01 05:47p4,287 engpar_h.txt 08/09/01 05:43p 7,688 Focu_h.txt 08/09/01 05:48p3,764 indus_h.txt 08/09/01 05:49p 69,191 rpmtbl_h.txt 08/09/01 05:47p96,378 scmd_c.txt 08/09/01 05:49p 7,414 SineTb_h.txt 08/09/01 05:46p8,819 sintrp_c.txt 08/09/01 05:45p 327,430 smain_c.txt 08/09/01 05:50p27,961 smain_h.txt 08/09/01 05:48p 97,596 sspin_c.txt 08/09/01 05:46p189,471 stint_c.txt 08/09/01 05:45p 57,381 stools_c.txt 08/09/01 05:51p2,185 stools_h.txt 08/09/01 05:51p 302,470 sutil_c.txt 08/09/01 05:51p30,265 sxtrn_h.txt 08/09/01 05:51p 11,063 TrackC_h.txt 08/09/01 05:49p25,479 XYram_h.txt 24 File(s) 1,990,561 bytes Total Files Listed: 24File(s) 1,990,561 bytes 0 bytes free

1. A method of calibrating operating parameters in an optical disk driveover a plurality of zones, the optical disk drive including a pluralityof photodetectors producing a corresponding plurality of photodetectorsignals, wherein the optical disk drive includes a plurality ofamplifiers corresponding to the plurality of photodetector signals suchthat each photodetector signal is individually gain-adjusted by itscorresponding amplifier, the plurality of amplifiers thereby producing aplurality of gain-adjusted photodetector signals, the method comprising:providing a digital signal processor configured to receive digitizedversions of the gain-adjusted photodetector signals and form a focusingerror signal (FES) and a tracking error signal (TES) from the digitizedversions, the digital signal processor configured with servo algorithmsthat process TES and FES to adjust focus and tracking in the opticaldisk drive; positioning the optical pick-up unit over a current zone,the current zone being one of the plurality of zones in an opticalmedia; performing calibration algorithms to optimize a gain value foreach of the amplifiers with respect to the current zone; and proceedingto a next zone, the next zone being another one of the plurality ofzones, unless all of the plurality of zones have been calibrated.
 2. Themethod of claim 1, wherein performing the calibration algorithmsincludes performing a tracking error signal offset calibration.
 3. Themethod of claim 1, wherein performing the calibration algorithmsincludes performing a tracking error signal gain calibration.
 4. Themethod of claim 1, wherein performing the calibration algorithmsincludes performing a non-linearity calibration.
 5. The method of claim1, wherein performing the calibration algorithms includes performing anotch filter calibration.
 6. The method of claim 1, wherein performingthe calibration algorithms includes performing a loop gain calibration.7. The method of claim 1, wherein performing the calibration algorithmsincludes performing a tracking error signal to focus error signal crosscoupling calibration.
 8. The method of claim 1, wherein the plurality ofzones includes a first zone having a writable portion and a second zonehaving a premastered portion.
 9. An optical disk drive, comprising: anoptical pick-up unit including a plurality of photodetectors; aplurality of amplifiers corresponding to the plurality of photodetectorssuch that each amplifier amplifies a photodetector output signal fromthe corresponding photodetector; an analog-to-digital converter coupledto receive signals from the amplifiers and digitize the received signalsto provide digitized detector signals; at least one processor coupled toreceive the digitized detector signals and form a focusing error signal(FES) and a tracking error signal (TES) from the digitized detectorsignals, the processor configured with servo algorithms that process TESand FES to calculate control signals to adjust focus and tracking in theoptical disk drive; and a driver coupled to control a position of theoptical pick-up unit in response to the control signals, wherein the atleast one processor executes an algorithm that calibrates operatingparameters over a plurality of zones by positioning the optical pick-upunit over a current zone, the current zone being one of the plurality ofzones on an optical media, performing calibration algorithms to optimizea gain value for each of the amplifiers with respect to the currentzone, and proceeding to a next zone, the next zone being another one ofthe plurality of zones, unless all of the plurality of zones have beencalibrated.
 10. The drive of claim 9, wherein the at least one processorfurther executes an algorithm that calibrates the operating parametersover a plurality of media types within each of the plurality of zones.11. The drive of claim 9, wherein the at least one processor furtherexecutes an algorithm that calibrates the operating parameters over aplurality of operating conditions over at least one of the plurality ofmedia types.